Transcutaneous analyte sensors, applicators therefor, and associated methods

ABSTRACT

The present embodiments relate generally to applicators of on-skin sensor assemblies for measuring an analyte in a host, as well as their method of use and manufacture. In some aspects, an applicator for applying an on-skin sensor assembly to a skin of a host is provided. The applicator includes an applicator housing, a needle carrier assembly comprising an insertion element configured to insert a sensor of the on-skin sensor assembly into the skin of the host, a holder releasably coupled to the needle carrier assembly and configured to guide the on-skin sensor assembly while coupled to the needle carrier assembly, and a drive assembly configured to drive the insertion element from a proximal starting position to a distal insertion position, and from the distal insertion position to a proximal retraction position.

INCORPORATION BY REFERENCE TO RELATED APPLICATIONS

Any and all priority claims identified in the Application Data Sheet, orany correction thereto, are hereby incorporated by reference under 37CFR 1.57. This application is a continuation of U.S. application Ser.No. 17/090,838, filed Nov. 5, 2020, which is a continuation of U.S.application Ser. No. 16/016,354, filed Jun. 22, 2018, now issued U.S.Pat. No. 10,863,944, issued on Dec. 15, 2020, which, in turn, claims thebenefit of U.S. Provisional Application No. 62/524,247, filed Jun. 23,2017 and U.S. Provisional Application No. 62/658,486, filed Apr. 16,2018. Each of the aforementioned applications is incorporated byreference herein in its entirety, and each is hereby expressly made apart of this specification.

FIELD

Systems and methods for measuring an analyte in a host are provided.More particularly, systems and methods are provided for applying atranscutaneous analyte measurement system to a host.

BACKGROUND

Diabetes mellitus is a disorder in which the pancreas cannot createsufficient insulin (Type I or insulin dependent) and/or in which insulinis not effective (Type 2 or non-insulin dependent). In the diabeticstate, the victim suffers from high blood sugar, which can cause anarray of physiological derangements associated with the deterioration ofsmall blood vessels, for example, kidney failure, skin ulcers, orbleeding into the vitreous of the eye. A hypoglycemic reaction (lowblood sugar) can be induced by an inadvertent overdose of insulin, orafter a normal dose of insulin or glucose-lowering agent accompanied byextraordinary exercise or insufficient food intake.

Conventionally, a person with diabetes carries a self-monitoring bloodglucose (SMBG) monitor, which typically requires uncomfortable fingerpricking methods. Due to the lack of comfort and convenience, a personwith diabetes normally only measures his or her glucose levels two tofour times per day. Unfortunately, such time intervals are spread so farapart that the person with diabetes likely finds out too late of ahyperglycemic or hypoglycemic condition, sometimes incurring dangerousside effects. Glucose levels may be alternatively monitored continuouslyby a sensor system including an on-skin sensor assembly. The sensorsystem may have a wireless transmitter which transmits measurement datato a receiver which can process and display information based on themeasurements.

The process of applying the sensor to the person is important for such asystem to be effective and user friendly. The application process shouldresult in the sensor assembly being attached to the person in a statewhere it is capable of sensing glucose level information, communicatingthe sensed data to the transmitter, and transmitting the glucose levelinformation to the receiver.

This Background is provided to introduce a brief context for the Summaryand Detailed Description that follow. This Background is not intended tobe an aid in determining the scope of the claimed subject matter nor beviewed as limiting the claimed subject matter to implementations thatsolve any or all of the disadvantages or problems presented above.

SUMMARY

The present systems and methods relate to systems and methods formeasuring an analyte in a host, and for applying a transcutaneousanalyte measurement system to a host. The various embodiments of thepresent systems and methods for applying the analyte measurement systemhave several features, no single one of which is solely responsible fortheir desirable attributes. Without limiting the scope of the presentembodiments as expressed by the claims that follow, their more prominentfeatures now will be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description,” one will understand how the features of thepresent embodiments provide the advantages described herein.

An applicator for applying an on-skin sensor assembly to a skin of ahost is provided. The applicator includes an applicator housing, aneedle carrier assembly, which includes an insertion element configuredto insert a sensor of the on-skin sensor assembly into the skin of thehost, a holder releasably coupled to the needle carrier assembly andconfigured to guide the on-skin sensor assembly while coupled to theneedle carrier assembly, and a drive assembly configured to drive theinsertion element from a proximal starting position to a distalinsertion position, and from the distal insertion position to a proximalretraction position.

In some embodiments, the on-skin sensor assembly includes an electronicsunit. In some embodiments, the sensor is connected to the electronicsunit in the applicator housing. In some embodiments, the holder isconfigured to release the on-skin sensor assembly after the sensor isinserted at least partially into the skin of the host. In someembodiments, the applicator further includes an activation elementconfigured to activate the drive assembly. In some embodiments, theactivation element includes a deflectable feature. In some embodiments,the deflectable feature is configured to provide resistance toactivation. In some embodiments, the deflectable feature is configuredto return the activation element to a starting position. In someembodiments, the activation element includes one of a button, a switch,a toggle, a slide, a trigger, and a knob. In some embodiments, theapplicator further includes a safety element configured to preventoperation of the activation element. In some embodiments, the safetyelement includes a tab coupled to the activation element by at least onefrangible member. In some embodiments, the distal direction and theproximal direction extend along an insertion axis of the insertionelement. In some embodiments, the holder includes an elastomer.

In a first aspect, the applicator housing includes a guide. The driveassembly includes a rotating drive element coupled to the needle carrierassembly and includes a pin configured to travel in the guide duringrotation of the rotating drive element, and a spring configured to, uponactivation of the drive assembly, rotate the rotating drive element in asingle rotational direction thereby driving the insertion element fromthe proximal starting position to the distal insertion position, andfrom the distal insertion position to the proximal retraction position.In some embodiments, the rotating drive element is configured to convertrotational motion into linear motion. In some embodiments, the rotatingdrive element includes a wheel cam. In some embodiments, the pin isradially offset from an axis of rotation of the rotating drive element.In some embodiments, the pin is positioned approximately 30 degrees froma bottom center orientation relative to the axis of rotation of therotating drive element when the insertion element is in the proximalstarting position. In some embodiments, the pin is positionedapproximately 180 degrees from a bottom center orientation relative tothe axis of rotation of the rotating drive element when the insertionelement is in the distal insertion position. In some embodiments, thepin is positioned approximately 330 degrees from a bottom centerorientation relative to the axis of rotation of the rotating driveelement when the needle carrier assembly is in the proximal retractedposition. In some embodiments, the pin travels in the guide in adirection perpendicular to a direction of extension of the insertionelement. In some embodiments, the guide includes a slot. In someembodiments, the slot is stationary during sensor insertion. In someembodiments, the slot includes a horizontal slot. In some embodiments,the slot includes a vertical slot configured to receive at least the pinof the rotating drive element when loaded through a bottom of theapplicator housing. In some embodiments, the applicator housing isstationary. In some embodiments, the rotating drive element furtherincludes a protrusion in contact with a retention element configured toprevent the rotating drive element from rotating. In some embodiments,the applicator further includes an activation element configured todeflect the retention element, thereby allowing the rotating driveelement to rotate. In some embodiments, the rotating drive elementfurther includes a protrusion configured to decouple the on-skin sensorassembly from the needle carrier assembly. In some embodiments, theprotrusion is configured to apply a force to the on-skin sensor assemblyduring rotation of the rotating drive element. In some embodiments, theprotrusion of the rotating drive element is configured to pass through aslot in the needle carrier assembly as the rotating drive elementrotates.

In a second aspect, the drive assembly includes a torsion spring. Thetorsion spring includes a first end coupled to the applicator housing,and a second end coupled to the needle carrier assembly. Upon activationof the drive assembly, the first end and the second end unwind inopposite directions, thereby driving the insertion element from theproximal starting position to the distal insertion position, and fromthe distal insertion position to the proximal retraction position. Insome embodiments, the first end and the second end unwinding in oppositedirections drives the torsion spring in an arc. In some embodiments, thearc extends in a direction perpendicular to the distal direction and theproximal direction. In some embodiments, a spool coupled to the torsionspring. In some embodiments, the torsion spring is wrapped around thespool. In some embodiments, the second end of the torsion spring isconfigured to drive the insertion element. In some embodiments, thetorsion spring is a double torsion spring. In some embodiments, thefirst end of the torsion spring is coupled to a protrusion of theapplicator housing. In some embodiments, the second end of the torsionspring is coupled to a protrusion of the needle carrier assembly.

In a third aspect, the drive assembly further includes a linkageelement, which includes a first end coupled to the first end of thetorsion spring, a second end coupled to the second end of the torsionspring, and a hinge substantially aligned with a winding axis of thetorsion spring. In some embodiments, the linkage element includes aflexible linkage.

In a fourth aspect, the drive assembly includes a linkage element, whichincludes a first end coupled to the applicator housing, a second endcoupled to the needle carrier assembly, and a hinge disposed between thefirst end and the second end. The drive assembly further includes atorsion spring, which includes a first end coupled to the needle carrierassembly, and a second end coupled to the linkage element between thesecond end and the hinge. Upon activation of the drive assembly, thesecond end is configured to drive the linkage element such that theinsertion element is driven from the proximal starting position to thedistal insertion position, and from the distal insertion position to theproximal retracted position.

In a fifth aspect, the drive assembly includes a linkage element, whichincludes a first end coupled to the applicator housing, a second endcoupled to the needle carrier assembly, and a hinge disposed between thefirst end and the second end. The drive assembly further includes atorsion spring, which includes a first end coupled to the applicatorhousing, and a second end coupled to the linkage element between thefirst end and the hinge. Upon activation of the drive assembly, thesecond end is configured to drive the linkage element such that theinsertion element is driven the proximal starting position to the distalinsertion position, and from the distal insertion position to theproximal retracted position.

In a sixth aspect, the drive assembly includes a linkage element, whichincludes a first end coupled to the applicator housing, a second endcoupled to the needle carrier assembly, and a hinge disposed between thefirst end and the second end. The drive assembly further includes anextension spring coupled to the linkage element. Upon activation of thedrive assembly, the extension spring is configured to drive the linkageelement such that the insertion element is driven in the distaldirection to the distal insertion position and in the proximal directionfrom the distal insertion position.

In a seventh aspect, the drive assembly includes a leaf spring, whichincludes a first end coupled to the applicator housing, and a second endcoupled to the needle carrier assembly. Upon activation of the driveassembly, the leaf spring is configured to decompress, thereby drivingthe insertion element at least in the distal direction to the distalinsertion position.

In an eighth aspect, the drive assembly includes a linkage element,which includes a first end coupled to the applicator housing, a secondend coupled to the needle carrier assembly, and a hinge disposed betweenthe first end and the second end. The drive assembly further includes aleaf spring, which includes a first end coupled to the needle carrierassembly, and a second end coupled to the linkage element between thesecond end and the hinge. Upon activation of the drive assembly, theleaf spring is configured to decompress, thereby driving the insertionelement in the distal direction to the distal insertion position and inthe proximal direction from the distal insertion position.

In a ninth aspect, the drive assembly includes a leaf spring, whichincludes a first end coupled to the applicator housing, and a second endcoupled to the needle carrier assembly. Upon activation of the driveassembly, the leaf spring is configured to decompress, thereby drivingthe insertion element at least in the distal direction to the distalinsertion position.

In a tenth aspect, the drive assembly includes a linkage element, whichincludes a first end coupled to the applicator housing, a second endcoupled to the needle carrier assembly; and a hinge disposed between thefirst end and the second end. The drive assembly further includes a leafspring, which includes a first end coupled to the needle carrierassembly, and a second end coupled to the linkage element between thesecond end and the hinge. Upon activation of the drive assembly, theleaf spring is configured to decompress, thereby driving the insertionelement in the distal direction to the distal insertion position and inthe proximal direction from the distal insertion position.

In an eleventh aspect, the drive assembly includes an insertion springconfigured to, upon activation of the drive assembly, drive theinsertion element in the distal direction to the distal insertionposition, and a retraction spring in contact with the needle carrierassembly and configured to drive the insertion element from the distalinsertion position to the proximal retracted position. In someembodiments, the insertion spring includes a compression spring. In someembodiments, the retraction spring includes a leaf spring. In someembodiments, the retraction spring is configured retract the insertionelement from the skin of the host. In some embodiments, upon activationof the drive assembly, a portion of energy stored in the insertionspring is transferred to the retraction spring as the insertion springdrives the insertion element in the distal direction. In someembodiments, the insertion spring includes a first end coupled to theapplicator housing and a second end coupled to the holder, and theholder is coupled to the needle carrier assembly while the insertionspring drives the insertion element in the distal direction to thedistal insertion position and decoupled from the needle carrier assemblywhen the retraction spring drives the insertion element in the proximaldirection from the distal insertion position. In some embodiments, theinsertion element is configured to travel in an arc when driven in thedistal direction and in the proximal direction.

In a twelfth aspect, the drive assembly includes a rotating driveelement, which includes a ridge configured to slide along a channel inthe needle carrier assembly, the ridge defining a variable cam patharound at least a portion of a circumference of the rotating driveelement, and a torsion spring configured to, upon activation of thedrive assembly, rotate the rotating drive element thereby driving theinsertion element in a distal direction to a distal insertion positionand in a proximal direction from the distal insertion position based onthe variable cam path. In some embodiments, the torsion spring isconfigured to, upon activation of the drive assembly, rotate therotating drive element in a single direction through an angle of greaterthan zero degrees and less than 360 degrees. In some embodiments, therotating drive element includes a barrel cam. In some embodiments, therotating drive element is configured to rotate in a plane substantiallyperpendicular to the proximal direction and the distal direction.

In a thirteenth aspect, the drive assembly includes a guide membercoupled to the applicator housing, a hub configured to slide along theguide member, the hub in contact with a reverse toggling element througha first portion of travel along the guide member and in contact with theneedle carrier assembly through a second portion of travel along theguide member. The reverse toggling element includes a fulcrum, a firstend in contact with the hub through the first portion of travel alongthe guide member, and a second end coupled with the needle carrierassembly. The drive assembly further includes a spring configured to,upon activation of the drive assembly drive the hub in a proximaldirection through the first portion of travel along the guide member,thereby driving the insertion element in the distal direction to thedistal insertion position, and drive the hub in the proximal directionthrough the second portion of travel along the guide member, therebydriving the insertion element in the proximal direction from the distalinsertion position.

In a fourteenth aspect, the drive assembly includes a first springconfigured to, upon activation of the drive assembly, drive the needlecarrier assembly in the distal direction to a distal insertion position,and a second spring configured to drive the needle carrier assembly inthe proximal direction from the distal insertion position. In someembodiments, the first spring and the second spring are precompressedbefore activation of the drive assembly. In some embodiments, at least aportion of energy stored in the first spring is transferred to thesecond spring as the needle carrier assembly is driven in the distaldirection to the distal insertion position.

In some embodiments, the holder includes at least one retention elementconfigured to immobilize the holder to the applicator housing upon theneedle carrier assembly reaching the distal insertion position. In someembodiments, the holder further includes a retention element configuredto releasably couple the on-skin sensor assembly to the holder as theneedle carrier assembly travels in the distal direction to the distalinsertion position, and decouple the on-skin sensor assembly from theholder as the needle carrier assembly travels in the proximal directionfrom the distal insertion position.

In some embodiments, the holder includes a retention element, whichincludes a first end and a second end. The first end is immobilized in aguide of the needle carrier assembly thereby releasably coupling thesecond end to the on-skin sensor assembly as the needle carrier assemblytravels in the distal direction to the distal insertion position, andthe first end is unseated from the guide of the needle carrier assemblythereby decoupling the second end from the on-skin sensor assembly asthe needle carrier assembly travels in the proximal direction from thedistal insertion position and separates from the holder.

In some embodiments, the needle carrier assembly includes a retentionelement releasably coupling the on-skin sensor assembly to the holder asthe needle carrier assembly travels in the distal direction to thedistal insertion position, and the retention element is configured todeform sufficiently to decouple from the on-skin sensor assembly as theneedle carrier assembly travels in the proximal direction from thedistal insertion position and separates from the holder.

In some embodiments, the holder includes a deformable retention elementreleasably coupling the on-skin sensor assembly to the holder, theneedle carrier assembly in contact with the deformable retention elementthereby preventing the deformable retention element from deforming asthe needle carrier assembly travels in the distal direction to thedistal insertion position. The needle carrier assembly separates fromthe holder as the needle carrier assembly travels in the proximaldirection from the distal insertion position thereby allowing theretention element to deform sufficiently to decouple from the on-skinsensor assembly.

In some embodiments, the needle carrier assembly includes a firstretention element configured to releasably couple the holder to theneedle carrier assembly, and a second retention element configured toreleasably couple the on-skin sensor assembly to one of the holder andthe needle carrier assembly.

In some embodiments, the insertion element includes a C-needle havingflared edges. In some embodiments, the insertion element includes adeflected-tip needle. In some embodiments, the insertion elementincludes a needle having a curvilinear profile configured tosubstantially track a path of insertion of the needle. In someembodiments, the insertion element includes a needle and the needlecarrier assembly further includes a needle hub configured as a passthrough for the needle during insertion of the sensor and is furtherconfigured to enclose a tip of the needle after insertion of the sensor.The insertion element further includes a needle spring configured todrive the needle hub to the tip of the needle after insertion of thesensor.

In some embodiments, the on-skin sensor assembly includes a fill portconfigured to receive a fluid or gel and a cannula configured to deliverthe fluid or gel through the skin of the host.

In some embodiments, the applicator further includes an elastomericsensor retention element coupled to the applicator housing at a firstend and coupled to at least one of the insertion element and the sensor.The elastomeric sensor retention element is configured to retain thesensor within the insertion element prior to activation of the driveassembly. In some embodiments upon activation, the insertion element isconfigured to progress in the proximal direction such that theelastomeric sensor retention element decouples from the at least one ofthe insertion element and the sensor.

In some embodiments, the applicator further includes a sensor retentionelement, which includes a tab configured to retain the sensor within theinsertion element prior to activation of the drive assembly.

In some embodiments, the applicator further includes a sensor retentionelement disposed against at least one of the insertion element and thesensor in a first position and configured to rotate away from theinsertion element and the sensor in a second position.

In some embodiments, the applicator further includes a sensor retentionsleeve disposed around at least a portion of the insertion element andthe sensor. The needle carrier assembly includes a tapered needle hubconfigured to split the sensor retention sleeve during insertion of thesensor.

In some embodiments, the sensor includes a strain relief featureconfigured to limit the sensor from bending at a bend radius smallerthan a predetermined bend radius. In some embodiments, the strain relieffeature includes an elastomeric material.

In some embodiments, the on-skin sensor assembly includes an open cavityconfigured to receive the sensor and provide an area for the sensor tobend from extending in a substantially horizontal direction to extendingin a substantially vertical direction. In some embodiments, the opencavity is configured to guide bodily fluid released from the host as aresult of insertion of the sensor at least partially into the skin ofthe host. In some embodiments, the on-skin sensor assembly includes awicking material configured to absorb a bodily fluid released from thehost as a result of insertion of the sensor at least partially into theskin of the host.

In a fifteenth aspect, a method for applying an on-skin sensor assemblyto skin of a host is provided. The method includes providing anapplicator, which includes an applicator housing, a needle carrierassembly includes an insertion element configured to insert a sensor ofthe on-skin sensor assembly into the skin of the host, a holderreleasably coupled to the needle carrier assembly and configured toguide the on-skin sensor assembly while coupled to the needle carrierassembly and a drive assembly and an activation element. The methodincludes activating the activation element, wherein activating theactivation element causes the drive assembly to drive the insertionelement in a distal direction to a distal insertion position and in aproximal direction from the distal insertion position to a proximalretraction position, thereby inserting the sensor of the on-skin sensorassembly at least partially into the skin of the host. In someembodiments, the distal direction and the proximal direction extendalong an insertion axis of the insertion element.

In some embodiments, the applicator housing includes a guide. The driveassembly includes a rotating drive element coupled to the needle carrierassembly and includes a pin configured to travel in the guide duringrotation of the rotating drive element, and a spring configured to, uponactivation of the drive assembly, rotate the rotating drive element in asingle rotational direction thereby driving the insertion element fromthe proximal starting position to the distal insertion position, andfrom the distal insertion position to the proximal retraction position.In some embodiments, the rotating drive element is configured to convertrotational motion into linear motion. In some embodiments, the rotatingdrive element includes a wheel cam. In some embodiments, the pin isradially offset from an axis of rotation of the rotating drive element.In some embodiments, the pin is positioned approximately 30 degrees froma bottom center orientation relative to the axis of rotation of therotating drive element when the insertion element is in the proximalstarting position. In some embodiments, the pin is positionedapproximately 180 degrees from a bottom center orientation relative tothe axis of rotation of the rotating drive element when the insertionelement is in the distal insertion position. In some embodiments, thepin is positioned approximately 330 degrees from a bottom centerorientation relative to the axis of rotation of the rotating driveelement when the needle carrier assembly is in the proximal retractedposition. In some embodiments, the guide includes a slot.

In some embodiments, the drive assembly includes a torsion spring, thetorsion spring includes a first end coupled to the applicator housing,and a second end coupled to the needle carrier assembly. Upon activationof the drive assembly, the first end and the second end unwind inopposite directions, thereby driving the insertion element from theproximal starting position to the distal insertion position, and fromthe distal insertion position to the proximal retraction position. Insome embodiments, the first end and the second end unwinding in oppositedirections drives the torsion spring in an arc. In some embodiments, thearc extends in a direction perpendicular to the distal direction and theproximal direction.

In some embodiments, the drive assembly includes an insertion springconfigured to, upon activation of the drive assembly, drive theinsertion element in the distal direction to the distal insertionposition, and a retraction spring in contact with the needle carrierassembly and configured to drive the insertion element from the distalinsertion position to the proximal retracted position. In someembodiments, the insertion spring includes a compression spring. In someembodiments, the retraction spring includes a leaf spring. In someembodiments, upon activation of the drive assembly, a portion of energystored in the insertion spring is transferred to the retraction springas the insertion spring drives the insertion element in the distaldirection. In some embodiments, the insertion spring includes a firstend coupled to the applicator housing and a second end coupled to theholder. The holder is coupled to the needle carrier assembly while theinsertion spring drives the insertion element in the distal direction tothe distal insertion position and decoupled from the needle carrierassembly when the retraction spring drives the insertion element in theproximal direction from the distal insertion position. In someembodiments, the insertion element is configured to travel in an arcwhen driven in the distal direction and in the proximal direction.

In some embodiments, the drive assembly includes a rotating driveelement, which includes a ridge configured to slide along a channel inthe needle carrier assembly, the ridge defining a variable cam patharound at least a portion of a circumference of the rotating driveelement, and a torsion spring configured to, upon activation of thedrive assembly, rotate the rotating drive element thereby driving theinsertion element in a distal direction to a distal insertion positionand in a proximal direction from the distal insertion position based onthe variable cam path. In some embodiments, the torsion spring isconfigured to, upon activation of the drive assembly, rotate therotating drive element in a single direction through an angle of greaterthan zero degrees and less than 360 degrees. In some embodiments, therotating drive element includes a barrel cam. In some embodiments, therotating drive element is configured to rotate in a plane substantiallyperpendicular to the proximal direction and the distal direction.

In some embodiments, the drive assembly includes a guide member coupledto the applicator housing, a hub configured to slide along the guidemember, the hub in contact with a reverse toggling element through afirst portion of travel along the guide member and in contact with theneedle carrier assembly through a second portion of travel along theguide member. The reverse toggling element includes a fulcrum, a firstend in contact with the hub through the first portion of travel alongthe guide member, and a second end coupled with the needle carrierassembly; The drive assembly further includes a spring configured to,upon activation of the drive assembly, drive the hub in a proximaldirection through the first portion of travel along the guide member,thereby driving the insertion element in the distal direction to thedistal insertion position, and drive the hub in the proximal directionthrough the second portion of travel along the guide member, therebydriving the insertion element in the proximal direction from the distalinsertion position.

In some embodiments, the drive assembly includes a first springconfigured to, upon activation of the drive assembly, drive the needlecarrier assembly in the distal direction to a distal insertion position,and a second spring configured to drive the needle carrier assembly inthe proximal direction from the distal insertion position. In someembodiments, at least a portion of energy stored in the first spring istransferred to the second spring as the needle carrier assembly isdriven in the distal direction to the distal insertion position.

In a sixteenth aspect, an applicator for applying an on-skin sensorassembly to a skin of a host is provided. The applicator includes aninsertion assembly configured to translate a needle carrier assembly andthe on-skin sensor assembly in a distal direction from an initialproximal position to a distal insertion position. The applicatorincludes a retraction assembly configured to translate the needlecarrier assembly in a proximal direction from the distal insertedposition to a proximal retracted position. The retraction assembly isconfigured to activate in response to the on-skin sensor assemblycontacting the skin of the host.

In some embodiments, the insertion assembly includes a first spring. Insome embodiments, the retraction assembly includes a second spring. Insome embodiments, the insertion assembly further includes a holderconfigured to guide the needle carrier assembly at least duringtranslation from the initial proximal position to the distal insertionposition. In some embodiments, the holder further includes at least oneretention element configured to retain the second spring at least duringinsertion. In some embodiments, the at least one retention element isdisposed along an outside of the second coil and configured to contactand retain a coil of the second spring. In some embodiments, the needlecarrier assembly further includes at least one backstop featureconfigured to prevent lateral deflection of the at least one retentionelement at least during insertion. In some embodiments, the at least onebackstop feature is configured not to contact the at least one retentionelement in the distal insertion position, thereby allowing the secondspring to deflect the at least one retention element and activate theretraction assembly. In some embodiments, the second spring isconfigured to exert a force sufficient to deflect the at least oneretention element in the distal insertion position when the on-skinsensor assembly is in contact with the skin of the host. In someembodiments, the applicator further includes an inner housing. In someembodiments, the applicator further includes an outer housing includingan activation element configured to activate the insertion assembly. Insome embodiments, the activation element is prevented from activatingthe insertion assembly until the outer housing is translated apredetermined distance in a distal direction with respect to the innerhousing. In some embodiments, the inner housing further includes anengagement element and the needle carrier assembly includes aprotrusion. The engagement element is configured to engage with theprotrusion upon the needle carrier assembly translating in a distaldirection beyond a predetermined threshold, thereby preventing theneedle carrier assembly from translating in the distal direction beyondthe predetermined threshold. In some embodiments, the engagement featureincludes a hook. In some embodiments, the needle carrier assemblyfurther includes a hub configured to couple an insertion element to theneedle carrier assembly. In some embodiments, the hub is furtherconfigured to couple to the on-skin sensor assembly.

In some embodiments, the insertion assembly and the retraction assemblyboth include the first spring. In some embodiments, the first spring isconfigured to exert a force between a holder and a deployment sleeve. Insome embodiments, the holder includes at least one retention elementconfigured to immobilize the holder to the deployment sleeve. In someembodiments, the applicator further includes a housing and an activationelement configured to deflect the at least one retention element,thereby enabling the first spring to translate the holder, the needlecarrier assembly and the on-skin sensor assembly from the proximalposition to the distal insertion position. In some embodiments, thehousing further includes at least one protrusion, and the deploymentsleeve includes at least one retention element configured to contact theat least one protrusion of the housing. In some embodiments, the firstspring is configured to exert a force sufficient to deflect the at leastone retention element of the deployment sleeve when the on-skin sensorassembly is in contact with the skin of the host, thereby freeing the atleast one retention element of the deployment sleeve from the at leastone protrusion of the housing. In some embodiments, the first spring isfurther configured to translate the deployment sleeve in the proximaldirection. In some embodiments, the needle carrier assembly furtherincludes a protrusion configured to contact the deployment sleeve,thereby causing the needle carrier assembly to translate in the proximaldirection.

In a seventeenth embodiment, a needle hub for applying an on-skin sensorassembly to a skin of a host is provided. The needle hub includes atleast one upper arm. The needle hub includes a base comprising ananti-rotation feature. The base is configured to be at least partiallydisposed in an aperture of the on-skin sensor assembly. The needle hubis configured to couple with an insertion element.

In some embodiments, the anti-rotation feature is configured to preventrotation of the base within the aperture. In some embodiments, theanti-rotation feature includes a key having a shape complementary to atleast a portion of the aperture. In some embodiments, the at least oneupper arm is configured to be disposed through an aperture in a needlecarrier assembly of an applicator. In some embodiments, the at least oneupper arm is configured to contact an upper surface of the needlecarrier assembly adjacent to the aperture in the needle carrierassembly. In some embodiments, the at least one upper arm is configuredto be disposed in a groove in the upper surface of the needle carrierassembly, thereby immobilizing the needle hub with respect to the needlecarrier assembly. In some embodiments, the at least one upper arm isflexible. In some embodiments, the at least one upper arm is configuredto flex radially inward. In some embodiments, the needle hub furtherincludes at least one lower arm. In some embodiments, the at least onelower arm is configured to contact a lower surface of the needle carrierassembly adjacent to an aperture in the needle carrier assembly. In someembodiments, the insertion element includes a needle. In someembodiments, the needle includes an open side configured to receive asensor of the on-skin sensor assembly. In some embodiments, the baseincludes a flat surface configured to mate with a top surface of theon-skin sensor assembly, thereby maintaining the insertion element in asubstantially perpendicular orientation to the top surface of theon-skin sensor assembly.

In an eighteenth embodiment, a method for applying an on-skin sensorassembly to skin of a host is provided. The method includes providing anapplicator. The applicator includes a housing comprising an activationelement. The applicator includes an insertion assembly. The applicatorincludes a retraction assembly. The method includes activating theactivation element. Activating the activation element causes theinsertion assembly to translate a needle carrier assembly and theon-skin sensor assembly in a distal direction from a proximal positionto a distal insertion position, thereby inserting a sensor of theon-skin sensor assembly at least partially into the skin of the host.Activating the activation element causes the retraction assembly totranslate the needle carrier assembly in a proximal direction from thedistal inserted position to a proximal retracted position. Theretraction assembly is configured to activate in response to on-skinsensor assembly contacting the skin of the host.

In some embodiments, the insertion assembly includes a first spring. Insome embodiments, the retraction assembly includes a second spring. Insome embodiments, the insertion assembly further includes a holderconfigured to guide the needle carrier assembly at least duringtranslation from the proximal position to the distal insertion position.In some embodiments, the holder further includes at least one retentionelement configured to retain the second spring at least duringinsertion. In some embodiments, the at least one retention element isdisposed along an outside of the second coil and configured to contactand retain a coil of the second spring. In some embodiments, the needlecarrier assembly further includes at least one backstop featureconfigured to prevent lateral deflection of the at least one retentionelement at least during insertion. In some embodiments, the at least onebackstop feature is configured not to contact the at least one retentionelement in the distal insertion position, thereby allowing the secondspring to deflect the at least one retention element and activate theretraction assembly. In some embodiments, the second spring isconfigured to exert a force sufficient to deflect the at least oneretention element in the distal insertion position when the on-skinsensor assembly is in contact with the skin of the host. In someembodiments, the second spring includes a tang extending along adiameter of second spring and wherein the at least one retention elementis disposed along an inside of the second spring and configured toretain the tang of the second spring. In some embodiments, the housingis an outer housing and the applicator further includes an innerhousing. In some embodiments, activating the activation element includestranslating the outer housing a predetermined distance in a distaldirection with respect to the inner housing. In some embodiments, theinner housing further includes an engagement element and the needlecarrier assembly includes a protrusion. The engagement element isconfigured to engage with the protrusion upon the needle carrierassembly translating in a distal direction beyond a predeterminedthreshold, thereby preventing the needle carrier assembly fromtranslating in the distal direction beyond the predetermined threshold.In some embodiments, the engagement feature includes a hook. In someembodiments, the needle carrier assembly further includes a needle hubconfigured to couple the insertion element to the needle carrierassembly.

In some embodiments, the insertion assembly and the retraction assemblyboth include the first spring. In some embodiments, the first spring isconfigured to exert a force between a holder and a deployment sleeve. Insome embodiments, the holder includes at least one retention elementconfigured to immobilize the holder to the deployment sleeve. In someembodiments, activating the activation element includes deflecting theat least one retention element of the holder, thereby enabling the firstspring to translate the holder, the needle carrier assembly and theon-skin sensor assembly from the proximal position to the distalinsertion position. In some embodiments, the housing further includes atleast one protrusion, and the deployment sleeve includes at least oneretention element configured to contact the at least one protrusion ofthe housing. In some embodiments, the first spring is configured toexert a force sufficient to deflect the at least one retention elementof the deployment sleeve when the on-skin sensor assembly is in contactwith the skin of the host, thereby freeing the at least one retentionelement of the deployment sleeve from the at least one protrusion of thehousing. In some embodiments, the first spring is further configured totranslate the deployment sleeve in the proximal direction. In someembodiments, the needle carrier assembly further includes a protrusionconfigured to contact the deployment sleeve, thereby causing the needlecarrier assembly to translate in the proximal direction.

In a nineteenth aspect, an applicator for applying an on-skin sensorassembly to a skin of a host is provided. The applicator includes afirst body releasably coupled to a needle. The applicator furtherincludes a second body releasably coupled to the first body by africtional engagement. The applicator further includes a springconfigured to provide a first force to the first body and second body.The first force can drive the first body and second body in a distaldirection. The frictional engagement can be configured to be decoupledby a counter force applied to the on-skin sensor assembly in an oppositedirection of the first force.

In some embodiments, the applicator further includes at least oneretention element configured to frictionally couple the second body tothe first body. In some embodiments, the at least one retention elementis formed integral with the second body. In some embodiments, the atleast one retention element is frictionally engaged against a wall ofthe first body. In some embodiments, the counter force decouples thefrictional engagement by displacing the at least one retention elementfrom the wall of the first body. In some embodiments, the wall is abackstop. In some embodiments, the wall is configured to prevent the atleast one retention element from deflecting.

In some embodiments, the frictional engagement is decoupled by thecounter force exceeding a force threshold. In some embodiments, theforce threshold is determined by the frictional force between the atleast one retention element and the first body. In some embodiments, thethreshold is at least 0.5 lbf. In some embodiments, the threshold is atleast 1 lbf.

In some embodiments, the first body is configured to retract in aproximal direction upon decoupling of the frictional engagement. In someembodiments, the applicator further includes a second spring. The secondspring can be configured to drive the first body in a proximaldirection. In some embodiments, the second spring is retained fromrelease by at least one retention element of the second body.

In some embodiments, the decoupling of the frictional engagement isconfigured to be independent of a distance between the on-skin sensorassembly and a distal end of the applicator. In some embodiments, thefirst body is configured to retract independent of the distance betweenthe on-skin sensor assembly and the distal end of the applicator. Insome embodiments, the counter force applied to the on-skin sensorassembly is provided by the skin of the host opposing the first force.In some embodiments, an interior of the applicator is configured toallow the skin of the host to reside within the interior. In someembodiments, the needle is configured to be inserted into the skin apredetermined depth. In some embodiments, the frictional engagement isconfigured to decouple at a range of distances between the on-skinsensor assembly and a distal end of the applicator.

This Summary is provided to introduce a selection of concepts furtherdescribed in the Detailed Description section. Elements or steps otherthan those described in this Summary are possible, and no element orstep is necessarily required. This Summary is not intended to identifykey features or essential features of the claimed subject matter, nor isit intended for use as an aid in determining the scope of the claimedsubject matter. The claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in any part ofthis disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages are described belowwith reference to the drawings, which are intended to illustrate, butnot to limit, the invention. In the drawings, like reference charactersdenote corresponding features consistently throughout similarembodiments.

FIG. 1 illustrates a schematic view of a continuous analyte sensorsystem, according to some embodiments.

FIGS. 2A-2B illustrate perspective views of an on-skin sensor assembly,according to some embodiments.

FIGS. 3A-3B illustrate perspective views of another on-skin sensorassembly, according to some embodiments.

FIG. 4 illustrates a cross-sectional view of the on-skin sensor assemblyof FIGS. 3A-3B, according to some embodiments.

FIG. 5 illustrates an exploded perspective view of the applicator ofFIG. 5, according to some embodiments.

FIG. 6A-6H illustrate cutaway views and perspective views of severalfeatures of the applicator of FIG. 5, according to some embodiments.

FIGS. 7A-7F illustrate several cutaway views of the applicator of FIG. 5during operation, according to some embodiments.

FIG. 8 illustrates a cutaway view of an applicator similar to theapplicator of FIG. 5, however, including an activation element on anupper side of an applicator housing, according to some embodiments.

FIG. 9 illustrates a cutaway view of an applicator similar to theapplicator of FIG. 5, however, including an activation element on amedial side of an applicator housing, according to some embodiments.

FIG. 10 illustrates a cutaway view of an applicator similar to theapplicator of FIG. 5, however, including an activation element on alower side of an applicator housing, according to some embodiments.

FIGS. 11A-11D and 11J illustrate perspective views while FIGS. 11E-11Hillustrate side cutaway views of steps for assembling the applicator ofFIG. 5, according to some embodiments.

FIG. 12 illustrates an exploded perspective view of another applicatorfor an on-skin sensor assembly of an analyte sensor system, according tosome embodiments.

FIG. 13A-13F illustrate perspective views and cutaway views of severalfeatures of the applicator of FIG. 12, according to some embodiments.

FIGS. 14A-14E illustrate several cross-sectional views of the applicatorof FIG. 12 during operation, according to some embodiments.

FIG. 15 illustrates a perspective view of an exemplary double torsionalspring for use in an applicator for an on-skin sensor assembly of ananalyte sensor system, according to some embodiments.

FIG. 16 illustrates a perspective view of another exemplary doubletorsional spring for use in an applicator for an on-skin sensor assemblyof an analyte sensor system, according to some embodiments.

FIG. 17 illustrates a perspective view of yet another exemplary doubletorsional spring for use in an applicator for an on-skin sensor assemblyof an analyte sensor system, according to some embodiments.

FIG. 18 illustrates a cutaway view of an alternative driving mechanismincluding a torsional spring and a living hinge for the applicator ofFIG. 12, according to some embodiments.

FIG. 19 illustrates a cutaway view of another alternative drivingmechanism including a torsional spring and a living hinge for theapplicator of FIG. 12, according to some embodiments.

FIG. 20 illustrates a cutaway view of yet another alternative drivingmechanism including a torsional spring and a living hinge for theapplicator of FIG. 12, according to some embodiments.

FIG. 21 illustrates a cutaway view of yet another alternative drivingmechanism including an extension spring and a living hinge for theapplicator of FIG. 12, according to some embodiments.

FIG. 22 illustrates a cutaway view of yet another alternative drivingmechanism including a leaf spring for the applicator of FIG. 12,according to some embodiments.

FIG. 23 illustrates a cutaway view of yet another alternative drivingmechanism including a leaf spring and a living hinge for the applicatorof FIG. 12, according to some embodiments.

FIGS. 24A-24F, 24H, 24J and 24L-24M illustrate cross-sectional viewswhile FIGS. 24G and 24K illustrate perspective views of steps forassembling the applicator of FIG. 12, according to some embodiments.

FIG. 25 illustrates an exploded perspective view of yet anotherapplicator for an on-skin sensor assembly of an analyte sensor system,according to some embodiments.

FIG. 26A-26D illustrate several cutaway perspective views and a bottomview of several features of the applicator of FIG. 25, according to someembodiments.

FIGS. 27A-27E illustrate several cross-sectional views of the applicatorof FIG. 25 during operation, according to some embodiments.

FIGS. 28A-28C and 28H illustrate several perspective views while FIGS.28D-28G illustrate cross-sectional views of assembling the applicator ofFIG. 25, according to some embodiments.

FIG. 29 illustrates an exploded perspective view of an applicator for anon-skin sensor assembly of an analyte sensor system, according to someembodiments.

FIG. 30 illustrates a cutaway view of a portion of the applicator ofFIG. 29, according to some embodiments.

FIG. 31 illustrates a cutaway view of yet another applicator for anon-skin sensor assembly of an analyte sensor system, according to someembodiments.

FIGS. 32A-34B illustrate exploded perspective views of yet anotherapplicator for an on-skin sensor assembly of an analyte sensor system,according to some embodiments.

FIGS. 33A-33E illustrate several perspective cutaway views of severalfeatures of the applicator of FIG. 32, according to some embodiments.

FIG. 34A-34D illustrate several cross-sectional views of the applicatorof FIG. 32 during operation, according to some embodiments.

FIG. 35A-35C illustrate cross-sectional views of an on-skin sensorassembly retention mechanism of the applicator of FIG. 32, according tosome embodiments.

FIG. 36A-36C illustrate cross-sectional views of another on-skin sensorassembly retention mechanism of the applicator of FIG. 32, according tosome embodiments.

FIG. 37A-37C illustrate cross-sectional views of yet another on-skinsensor assembly retention mechanism of the applicator of FIG. 32,according to some embodiments.

FIG. 38 illustrates a perspective view of an applicator similar to thoseshown in FIG. 32, including an activation element on a side of thehousing, according to some embodiments.

FIG. 39 illustrates a cutaway perspective view of a portion of theapplicator of FIG. 38, according to some embodiments.

FIGS. 40A-40G illustrate several perspective views of steps forassembling the applicator of FIG. 32, according to some embodiments.

FIGS. 41A-41B illustrate cross-sectional views an exemplary on-skinsensor assembly retention mechanism of an applicator for an analytesensor system, according to some embodiments.

FIGS. 42A-42B illustrate cross-sectional views of another exemplaryon-skin sensor assembly retention mechanism of an applicator for ananalyte sensor system, according to some embodiments.

FIGS. 43A-43B illustrate cross-sectional views of yet another exemplaryon-skin sensor assembly retention mechanism of an applicator for ananalyte sensor system, according to some embodiments.

FIG. 44 illustrates a perspective view of a portion of another exemplaryon-skin sensor assembly retention mechanism of an applicator for ananalyte sensor system, according to some embodiments.

FIG. 45 illustrates a perspective view of portion of an exemplaryon-skin sensor assembly retention mechanism of an applicator for ananalyte sensor system, according to some embodiments.

FIG. 46 illustrates a perspective view of a portion of an exemplaryon-skin sensor assembly retention mechanism of an applicator for ananalyte sensor system, according to some embodiments.

FIG. 47 illustrates a cross-section of a kinked needle for use in anapplicator for an analyte sensor system, according to some embodiments.

FIGS. 48A-48B illustrate a cross-section and a plan view, respectively,of a flared C-needle for use in an applicator for an analyte sensorsystem, according to some embodiments.

FIG. 49 illustrates a perspective view of a deflected-tip needle for usein an applicator for an analyte sensor system, according to someembodiments.

FIG. 50 illustrates a perspective view of a curved needle for use in anapplicator for an analyte sensor system, according to some embodiments.

FIGS. 51A-51B illustrate cutaway views of a needle hub of an applicatorfor an analyte sensor system, according to some embodiments.

FIGS. 52A-52B illustrate a cross-sectional view and a plan view,respectively, of an infusion cannula integrated into an on-skin sensorassembly of an analyte sensor system, according to some embodiments.

FIG. 53 illustrates a cross-sectional view of a sensor retentionmechanism for an applicator for an analyte sensor system, according tosome embodiments.

FIG. 54 illustrates a perspective view of another sensor retentionmechanism for an applicator for an analyte sensor system, according tosome embodiments.

FIG. 55 illustrates a cutaway view of another sensor retention mechanismfor an applicator for an analyte sensor system, according to someembodiments.

FIGS. 56A-56B illustrate perspective views of another sensor retentionelement for an applicator for an analyte sensor system, according tosome embodiments.

FIG. 57 illustrates a cross-sectional view of yet another sensorretention element for an applicator for an analyte sensor system,according to some embodiments.

FIG. 58 illustrates a cross-sectional view of yet another sensorretention element for an applicator for an analyte sensor system,according to some embodiments.

FIGS. 59A-59B illustrate cross-sectional views of yet another sensorretention element for an applicator for an analyte sensor system,according to some embodiments.

FIG. 60 illustrates a cutaway view of an on-skin sensor assembly havingat least a portion of a sensor potted in a flexible material, accordingto some embodiments.

FIG. 61 illustrates a cutaway view of an on-skin sensor assemblycomprising an open cavity configured to allow a larger bend radius in asensor, according to some embodiments.

FIG. 62 illustrates a cutaway view of an on-skin sensor assemblycomprising an open cavity configured to allow a larger bend radius in asensor, according to some embodiments.

FIG. 63 illustrates a cutaway view of an on-skin sensor assemblycomprising an open cavity configured to allow a larger bend radius in asensor, according to some embodiments.

FIGS. 64A-64B illustrate a battery engagement feature for an on-skinsensor assembly, according to some embodiments.

FIG. 65 illustrates a flowchart of a method for applying an on-skinsensor assembly to skin of a host, according to some embodiments.

FIG. 66 illustrates exemplary mechanisms for several features of anapplicator configured to apply an on-skin sensor assembly to skin of ahost, according to some embodiments.

FIG. 67 illustrates exemplary sterilization, packaging and sealingfeatures of an applicator configured to apply an on-skin sensor assemblyto skin of a host, according to some embodiments.

FIG. 68 illustrates a top perspective view of an on-skin sensorassembly, according to some embodiments.

FIG. 69 illustrates a bottom perspective view of the on-skin sensorassembly of FIG. 68, according to some embodiments.

FIG. 70 illustrates a cross-sectional view of the on-skin sensorassembly of FIG. 68, according to some embodiments.

FIG. 71 illustrates yet another applicator for an on-skin sensorassembly of an analyte sensor system, according to some embodiments.

FIG. 72 illustrates an exploded perspective view of the applicator ofFIG. 71, according to some embodiments.

FIGS. 73A-73C illustrate several cross-sectional views of the applicatorof FIGS. 71 and 72, taken along the section line A-A′ of FIG. 71, duringoperation, according to some embodiments.

FIGS. 74A-74C illustrate several cross-sectional views of the applicatorof FIGS. 71 and 72, taken along the section line B-B′ of FIG. 71, duringoperation, according to some embodiments.

FIGS. 75A and 75B illustrate magnified views of some features of theapplicator of FIGS. 71 and 72, according to some embodiments.

FIGS. 76A and 76B illustrate magnified views of some features of theapplicator of FIGS. 71 and 72, according to some embodiments.

FIG. 77 illustrates a perspective partial cutaway view of the needlecarrier assembly, hub, and on-skin sensor assembly of the applicator ofFIGS. 71 and 72, according to some embodiments.

FIG. 78 illustrates a cross-sectional view of the hub and on-skin sensorassembly of the applicator of FIGS. 71 and 72, according to someembodiments.

FIG. 79 illustrates a top view of a portion of the needle carrierassembly and hub of FIGS. 71 and 72, according to some embodiments.

FIGS. 80A and 80B illustrate perspective views of locking features forneedles for use in an applicator for an analyte sensor system, accordingto some embodiments.

FIGS. 81A-81C illustrate several cross-sectional views, and variousfeatures and operating positions, of yet another applicator for anon-skin sensor assembly of an analyte sensor system, according to someembodiments.

FIG. 81D illustrates a perspective view of various features of theapplicator of FIGS. 81A-81D, according to some embodiments.

FIGS. 82A-82D illustrate several cross-sectional views, and variousfeatures and operating positions, of yet another applicator for anon-skin sensor assembly of an analyte sensor system, according to someembodiments.

FIG. 83 illustrates a cross-sectional view of an applicator comprising adeformable layer disposed over an activation element, according to someembodiments.

FIG. 84 illustrates a perspective view of an applicator utilizing atwist-to-activate activation mechanism, according to some embodiments.

FIG. 85 illustrates a cross-sectional view of an applicator comprising atop-mounted activation element, according to some embodiments.

FIG. 86 illustrates relationships between the axle, insertion element,and a circular arc travelled by the insertion element of at least FIG.26C during insertion and retraction, according to some embodiments.

FIG. 87 illustrates a cross-sectional view of on-skin sensor assembly ofFIGS. 3A, 3B and 4, further comprising an upper patch 328, according tosome embodiments.

FIGS. 88A-88B illustrate perspective views of another optional batteryconnection feature for an on-skin sensor assembly, in accordance withsome embodiments.

FIG. 89 illustrates a flowchart of another method for applying anon-skin sensor assembly to skin of a host, according to someembodiments.

FIG. 90 illustrates a magnified view of some features of the applicatorof FIGS. 71 and 72, according to some embodiments.

FIG. 91 illustrates a perspective view of an on-skin sensor assembly,according to some embodiments

DETAILED DESCRIPTION

The following description and examples illustrate some exampleembodiments in detail. Those of skill in the art will recognize thatthere are numerous variations and modifications of this disclosureencompassed by its scope. Accordingly, the description of a certainexample embodiment should not be deemed to limit the scope of thepresent disclosure.

System Introduction

FIG. 1 is a diagram depicting an example continuous analyte monitoringsystem 100 including an analyte sensor system 102 comprising an on-skinsensor assembly 160 configured to be fastened to the skin of a host viaa base (not shown). Analyte sensor system 102 is operatively connectedto a host and a plurality of display devices 110-114 according tocertain aspects of the present disclosure. Example display devices110-114 may include computers such as smartphones, smartwatches, tabletcomputers, laptop computers, and desktop computers. In some embodiments,display devices 110-114 may be Apple Watches, iPhones, and iPads made byApple Inc., or Windows or Google devices. It should be noted thatdisplay device 114 alternatively or in addition to being a displaydevice, may be a medicament delivery device that can act cooperativelywith analyte sensor system 102 to deliver medicaments to the host.Analyte sensor system 102 may include a sensor electronics module 140and a continuous analyte sensor 138 associated with sensor electronicsmodule 140. Sensor electronics module 140 may be in direct wirelesscommunication with one or more of the plurality of display devices110-114 via wireless communications signals. As will be discussed ingreater detail below, display devices 110-114 may also communicateamongst each other and/or through each other to analyte sensor system102. For ease of reference, wireless communications signals from analytesensor system 102 to display devices 110-114 can be referred to as“uplink” signals 128. Wireless communications signals from, e.g.,display devices 110-114 to analyte sensor system 102 can be referred toas “downlink” signals 130. Wireless communication signals between two ormore of display devices 110-114 may be referred to as “crosslink”signals 132. Additionally, wireless communication signals can includedata transmitted by one or more of display devices 110-113 via“long-range” uplink signals 136 (e.g., cellular signals) to one or moreremote servers 190 or network entities, such as cloud-based servers ordatabases, and receive long-range downlink signals 142 transmitted byremote servers 190.

In embodiments shown by FIG. 1, one of the plurality of display devicesmay be a custom display device 111 specially designed for displayingcertain types of displayable sensor information associated with analytevalues received from the sensor electronics module 126 (e.g., anumerical value and an arrow, in some embodiments). In some embodiments,one of the plurality of display devices may be a handheld device 112,such as a mobile phone based on the Android, iOS operating system orother operating system, a palm-top computer and the like, where handhelddevice 112 may have a relatively larger display and be configured todisplay a graphical representation of the continuous sensor data (e.g.,including current and historic data). Other display devices can includeother hand-held devices, such as a tablet 113, a smart watch 110, amedicament delivery device 114, a blood glucose meter, and/or a desktopor laptop computer.

It should be understood that in the case of display device 134e, whichmay be a medicament delivery device in addition to or instead of adisplay device, the alerts and/or sensor information provided bycontinuous analyte sensor 122 vis-à-vis sensor electronics module 126,can be used to initiate and/or regulate the delivery of the medicamentto host 120.

During use, a sensing portion of sensor 138 may be disposed under thehost's skin and a contact portion of sensor 138 can be electricallyconnected to electronics unit 140. Electronics unit 140 can be engagedwith a housing (e.g., a base) which is attached to an adhesive patchfastened to the skin of the host. In some embodiments, electronics unit140 is integrally formed with the housing. Furthermore, electronics unit140 may be disposable and directly coupled to the adhesive patch.

Continuous analyte sensor system 100 can include a sensor configurationthat provides an output signal indicative of a concentration of ananalyte. The output signal including (e.g., sensor data, such as a rawdata stream, filtered data, smoothed data, and/or otherwise transformedsensor data) is sent to the receiver.

In some embodiments, analyte sensor system 100 includes a transcutaneousglucose sensor, such as is described in U.S. Patent Publication No.US-2011-0027127-A1, the entire contents of which are hereby incorporatedby reference. In some embodiments, sensor system 100 includes acontinuous glucose sensor and comprises a transcutaneous sensor (e.g.,as described in U.S. Pat. No. 6,565,509, as described in U.S. Pat. No.6,579,690, and/or as described in U.S. Pat. No. 6,484,046). The contentsof U.S. Pat. Nos. 6,565,509, 6,579,690, and 6,484,046 are herebyincorporated by reference in their entirety.

Various signal processing techniques and glucose monitoring systemembodiments suitable for use with the embodiments described herein aredescribed in U.S. Patent Publication No. US-2005-0203360-A1 and U.S.Patent Publication No. US-2009-0192745-A1, the contents of which arehereby incorporated by reference in their entirety. The sensor canextend through a housing, which can maintain sensor 138 on, in or underthe skin and/or can provide for electrical connection of sensor 138 tosensor electronics in electronics unit 140.

In some embodiments, description of a base, a housing, a wearable,and/or a transmitter of on-skin sensor assembly 160 may beinterchangeable. In other embodiments, a base and a housing of on-skinsensor assembly 160 may be different in the sense that they may beseparate components from sensor electronics module 140, e.g., from atransmitter or receiver.

In several embodiments, sensor 138 is in a form of a wire. A distal endof the wire can be formed, e.g., having a conical shape (to facilitateinserting the wire into the tissue of the host). Sensor 138 can includean elongated conductive body, such as an elongated conductive core(e.g., a metal wire) or an elongated conductive core coated with one,two, three, four, five, or more layers of material, each of which may ormay not be conductive. The elongated sensor may be long and thin, yetflexible and strong. For example, in some embodiments, the smallestdimension of the elongated conductive body is less than 0.1 inches, lessthan 0.075 inches, less than 0.05 inches, less than 0.025 inches, lessthan 0.01 inches, less than 0.004 inches, less than 0.002 inches, lessthan 0.001 inches, and/or less than 0.0005 inches.

Sensor 138 may have a circular cross section. In some embodiments, thecross section of the elongated conductive body can be ovoid,rectangular, triangular, polyhedral, star-shaped, C-shaped, T-shaped,X-shaped, Y-shaped, irregular, or the like. In some embodiments, aconductive wire electrode is employed as a core. In other embodiments,sensor 138 may be disposed on a substantially planar substrate. To suchan electrode, one or two additional conducting layers may be added(e.g., with intervening insulating layers provided for electricalisolation). The conductive layers can be comprised of any suitablematerial. In certain embodiments, it may be desirable to employ aconductive layer comprising conductive particles (i.e., particles of aconductive material) in a polymer or other binder.

In some embodiments, the materials used to form the elongated conductivebody (e.g., stainless steel, titanium, tantalum, platinum,platinum-iridium, iridium, certain polymers, and/or the like) can bestrong and hard, and therefore can be resistant to breakage. Forexample, in several embodiments, the ultimate tensile strength of theelongated conductive body is greater than 80 kPsi and less than 140kPsi, and/or the Young's modulus of the elongated conductive body isgreater than 160 GPa and less than 220 GPa. The yield strength of theelongated conductive body can be greater than 58 kPsi and less than 2200kPsi.

Electronics unit 140 can be releasably or permanently coupled to sensor138. Electronics unit 140 can include electronic circuitry associatedwith measuring and processing the continuous analyte sensor data.Electronics unit 140 can be configured to perform algorithms associatedwith processing and calibration of the sensor data. For example,electronics unit 140 can provide various aspects of the functionality ofa sensor electronics module as described in U.S. Patent Publication No.US-2009-0240120-A1 and U.S. Patent Publication No. US-2012-0078071-A1,the entire contents of which are incorporated by reference herein.Electronics unit 140 may include hardware, firmware, and/or softwarethat enable measurement of levels of the analyte via a glucose sensor,such as sensor 138.

For example, electronics unit 140 can include a potentiostat, a powersource for providing power to sensor 138, signal processing components,data storage components, and a communication module (e.g., a telemetrymodule) for one-way or two-way data communication between electronicsunit 140 and one or more receivers, repeaters, and/or display devices,such as devices 110-114. Electronic components can be affixed to aprinted circuit board (PCB), or the like, and can take a variety offorms. The electronic components can take the form of an integratedcircuit (IC), such as an Application-Specific Integrated Circuit (ASIC),a microcontroller, and/or a processor. The electronics unit 140 mayinclude sensor electronics that are configured to process sensorinformation, such as storing data, analyzing data streams, calibratinganalyte sensor data, estimating analyte values, comparing estimatedanalyte values with time-corresponding measured analyte values,analyzing a variation of estimated analyte values, and the like.Examples of systems and methods for processing sensor analyte data aredescribed in more detail in U.S. Pat. Nos. 7,310,544, 6,931,327, U.S.Patent Publication No. 2005-0043598-A1, U.S. Patent Publication No.2007-0032706-A1, U.S. Patent Publication No. 2007-0016381-A1, U.S.Patent Publication No. 2008-0033254-A1, U.S. Patent Publication No.2005-0203360-A1, U.S. Patent Publication No. 2005-0154271-A1, U.S.Patent Publication No. 2005-0192557-A1, U.S. Patent Publication No.2006-0222566-A1, U.S. Patent Publication No. 2007-0203966-A1 and U.S.Patent Publication No. 2007-0208245-A1, the contents of which are herebyincorporated by reference in their entirety. Electronics unit 140 maycommunicate with the devices 110-114, and/or any number of additionaldevices, via any suitable communication protocol. Example communicationmethods or protocols include radio frequency; Bluetooth; universalserial bus; any of the wireless local area network (WLAN) communicationstandards, including the IEEE 802.11, 802.15, 802.20, 802.22 and other802 communication protocols; ZigBee; wireless (e.g., cellular)telecommunication; paging network communication; magnetic induction;satellite data communication; a proprietary communication protocol, opensource communication protocol, and/or any suitable wirelesscommunication method.

Additional sensor information is described in U.S. Pat. Nos. 7,497,827and 8,828,201. The entire contents of U.S. Pat. Nos. 7,497,827 and8,828,201 are incorporated by reference herein.

Any sensor shown or described herein can be an analyte sensor; a glucosesensor; and/or any other suitable sensor. A sensor described in thecontext of any embodiment can be any sensor described herein orincorporated by reference. Sensors shown or described herein can beconfigured to sense, measure, detect, and/or interact with any analyte.

As used herein, the term “analyte” is a broad term, and is to be givenits ordinary and customary meaning to a person of ordinary skill in theart (and is not to be limited to a special or customized meaning), andrefers without limitation to a substance or chemical constituent in abiological fluid (for example, blood, interstitial fluid, cerebralspinal fluid, lymph fluid, urine, sweat, saliva, etc.) that can beanalyzed. Analytes can include naturally occurring substances,artificial substances, metabolites, or reaction products.

In some embodiments, the analyte for measurement by the sensing regions,devices, systems, and methods is glucose. However, other analytes arecontemplated as well, including, but not limited to ketone bodies;Acetyl Co A; acarboxyprothrombin; acylcarnitine; adenine phosphoribosyltransferase; adenosine deaminase; albumin; alpha-fetoprotein; amino acidprofiles (arginine (Krebs cycle), histidine/urocanic acid, homocysteine,phenylalanine/tyrosine, tryptophan); andrenostenedione; antipyrine;arabinitol enantiomers; arginase; benzoylecgonine (cocaine);biotinidase; biopterin; c-reactive protein; carnitine; carnosinase; CD4;ceruloplasmin; chenodeoxycholic acid; chloroquine; cholesterol;cholinesterase; cortisol; testosterone; choline; creatine kinase;creatine kinase MM isoenzyme; cyclosporin A; d-penicillamine;de-ethylchloroquine; dehydroepiandrosterone sulfate; DNA (acetylatorpolymorphism, alcohol dehydrogenase, alpha 1-antitrypsin, cysticfibrosis, Duchenne/Becker muscular dystrophy, glucose-6-phosphatedehydrogenase, hemoglobin A, hemoglobin S, hemoglobin C, hemoglobin D,hemoglobin E, hemoglobin F, D-Punjab, beta-thalassemia, hepatitis Bvirus, HCMV, HIV-1, HTLV-1, Leber hereditary optic neuropathy, MCAD,RNA, PKU, Plasmodium vivax, sexual differentiation, 21-deoxycortisol);desbutylhalofantrine; dihydropteridine reductase; diptheria/tetanusantitoxin; erythrocyte arginase; erythrocyte protoporphyrin; esterase D;fatty acids/acylglycines; triglycerides; glycerol; free B-humanchorionic gonadotropin; free erythrocyte porphyrin; free thyroxine(FT4); free tri-iodothyronine (FT3); fumarylacetoacetase;galactose/gal-1-phosphate; galactose-1-phosphate uridyltransferase;gentamicin; glucose-6-phosphate dehydrogenase; glutathione; glutathioneperioxidase; glycocholic acid; glycosylated hemoglobin; halofantrine;hemoglobin variants; hexosaminidase A; human erythrocyte carbonicanhydrase I; 17-alpha-hydroxyprogesterone; hypoxanthine phosphoribosyltransferase; immunoreactive trypsin; lactate; lead; lipoproteins ((a),B/A-1, β); lysozyme; mefloquine; netilmicin; phenobarbitone; phenytoin;phytanic/pristanic acid; progesterone; prolactin; prolidase; purinenucleoside phosphorylase; quinine; reverse tri-iodothyronine (rT3);selenium; serum pancreatic lipase; sissomicin; somatomedin C; specificantibodies (adenovirus, anti-nuclear antibody, anti-zeta antibody,arbovirus, Aujeszky's disease virus, dengue virus, Dracunculusmedinensis, Echinococcus granulosus, Entamoeba histolytica, enterovirus,Giardia duodenalisa, Helicobacter pylori, hepatitis B virus, herpesvirus, HIV-1, IgE (atopic disease), influenza virus, Leishmaniadonovani, leptospira, measles/mumps/rubella, Mycobacterium leprae,Mycoplasma pneumoniae, Myoglobin, Onchocerca volvulus, parainfluenzavirus, Plasmodium falciparum, poliovirus, Pseudomonas aeruginosa,respiratory syncytial virus, rickettsia (scrub typhus), Schistosomamansoni, Toxoplasma gondii, Trepenoma pallidium, Trypanosomacruzi/rangeli, vesicular stomatis virus, Wuchereria bancrofti, yellowfever virus); specific antigens (hepatitis B virus, HIV-1); acetone(e.g., succinylacetone); acetoacetic acid; sulfadoxine; theophylline;thyrotropin (TSH); thyroxine (T4); thyroxine-binding globulin; traceelements; transferrin; UDP-galactose-4-epimerase; urea; uroporphyrinogenI synthase; vitamin A; white blood cells; and zinc protoporphyrin.

Salts, sugar, protein, fat, vitamins, and hormones naturally occurringin blood or interstitial fluids can also constitute analytes in certainembodiments. The analyte can be naturally present in the biologicalfluid or endogenous, for example, a metabolic product, a hormone, anantigen, an antibody, and the like. Alternatively, the analyte can beintroduced into the body or exogenous, for example, a contrast agent forimaging, a radioisotope, a chemical agent, a fluorocarbon-basedsynthetic blood, or a drug or pharmaceutical composition, including butnot limited to insulin; glucagon; ethanol; cannabis (marijuana,tetrahydrocannabinol, hashish); inhalants (nitrous oxide, amyl nitrite,butyl nitrite, chlorohydrocarbons, hydrocarbons); cocaine (crackcocaine); stimulants (amphetamines, methamphetamines, Ritalin, Cylert,Preludin, Didrex, PreState, Voranil, Sandrex, Plegine); depressants(barbiturates, methaqualone, tranquilizers such as Valium, Librium,Miltown, Serax, Equanil, Tranxene); hallucinogens (phencyclidine,lysergic acid, mescaline, peyote, psilocybin); narcotics (heroin,codeine, morphine, opium, meperidine, Percocet, Percodan, Tussionex,Fentanyl, Darvon, Talwin, Lomotil); designer drugs (analogs of fentanyl,meperidine, amphetamines, methamphetamines, and phencyclidine, forexample, Ecstasy); anabolic steroids; and nicotine. The metabolicproducts of drugs and pharmaceutical compositions are also contemplatedanalytes. Analytes such as neurochemicals and other chemicals generatedwithin the body can also be analyzed, such as, for example, ascorbicacid, uric acid, dopamine, noradrenaline, 3-methoxytyramine (3MT),3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA),5-hydroxytryptamine (5HT), 5-hydroxyindoleacetic acid (FHIAA), andintermediaries in the Citric Acid Cycle.

Many embodiments described herein may use an adhesive to couple a baseor housing, a sensor module, a transmitter or electronics unit, and/or asensor to a host (e.g., to skin of the host). The adhesive can beconfigured for adhering to skin. The adhesive can include a pad (e.g.,that is located between the adhesive and the base). Additional adhesiveinformation, including adhesive pad information, is described in U.S.patent application Ser. No. 14/835,603, which was filed on Aug. 25,2015. The entire contents of U.S. patent application Ser. No. 14/835,603are incorporated by reference herein.

As noted above, systems can apply an on-skin sensor assembly to the skinof a host. The on-skin sensor assembly may include a base that comprisesan adhesive to couple a glucose sensor to the skin. Other methods arecontemplated such as a strap, e.g., a watch band.

Any of the features described in the context of at least FIG. 1 can beapplicable to all aspects and embodiments identified herein. Moreover,any of the features of an embodiment is independently combinable, partlyor wholly with other embodiments described herein in any way, e.g., one,two, or three or more embodiments may be combinable in whole or in part.Further, any of the features of an embodiment may be made optional toother aspects or embodiments. Any aspect or embodiment of a method canbe performed by a system or apparatus of another aspect or embodiment,and any aspect or embodiment of a system can be configured to perform amethod of another aspect or embodiment.

Throughout this disclosure, reference is made to an on-skin sensorassembly, which may also be described as a wearable. Such on-skin sensorassemblies (see FIGS. 1-4 and 68-70) may be disposable or reusable andmay (see FIGS. 68-70) or may not (see FIGS. 2-4) comprise a base or baseplate. In some embodiments, on-skin sensor assemblies having a baseplate (e.g., FIGS. 68-70) may be reusable, whereas on-skin sensorassemblies without a base plate (e.g., FIGS. 2-4) may be disposable.Although FIG. 1 has already been discussed with respect to on-skinsensor assembly 160, FIGS. 2A-4 and 68-70 describe at least some otherembodiments of an on-skin sensor assembly.

FIG. 2A illustrates a perspective view of an on-skin sensor assembly260, in accordance with some embodiments. On-skin sensor assembly 260may comprise an outer housing comprising a first, top portion 292 and asecond, lower portion 294. In some embodiments, the outer housing maycomprise a clamshell design. On-skin sensor assembly 260 may includesimilar components as electronics unit 140 described above in FIG. 1(e.g. a potentiostat, a power source for providing power to sensor 138,signal processing components, data storage components, and acommunication module (e.g., a telemetry module) for one-way or two-waydata communication, a printed circuit board (PCB), an integrated circuit(IC), an Application-Specific Integrated Circuit (ASIC), amicrocontroller, and/or a processor). The outer housing may feature alarge rounded body having tapered end opposite the large rounded body.The outer housing may further comprise an aperture 296 disposed at thetapered end of the outer housing and adapted for sensor 238 and needleinsertion. Aperture 296 may be an opening featuring a U-shaped channelextending through the tapered end of the outer housing. On-skin sensorassembly 260 may further comprise an adhesive patch 226 configured tosecure on-skin sensor assembly 260 to skin of the host. As shown,adhesive patch 226 may feature an aperture 298 having a similar shape asaperture 296 and substantially aligned with aperture 296. Sensor 238 maybe configured to at least partially extend through apertures 296 and298. In some embodiments, adhesive patch 226 may comprise an adhesivesuitable for skin adhesion, for example a pressure sensitive adhesive(e.g., acrylic, rubber-based, or other suitable type) bonded to acarrier substrate (e.g., spun lace polyester, polyurethane film, orother suitable type) for skin attachment, though any suitable type ofadhesive is also contemplated.

On-skin sensor assembly 260 may be attached to the host with use of anapplicator adapted to provide convenient and secure application. Such anapplicator may also be used for inserting sensor 238 through the host'sskin, and/or connecting sensor 238 to the electronics unit. Once sensor238 has been inserted into the skin (and is connected to the electronicsunit), the sensor assembly can detach from the applicator.

FIG. 2B illustrates a bottom perspective view of on-skin sensor assembly260 of FIG. 2A. FIG. 2B illustrates aperture 296 disposed to a side ofthe outer housing, and aperture 298, each adapted for sensor 238 andneedle insertion.

FIG. 3A illustrates a perspective view of an on-skin sensor assembly360, in accordance with some embodiments. On-skin sensor assembly 360may comprise an outer housing comprising a first, top portion 392 and asecond, lower portion 394. In some embodiments, the outer housing maycomprise a clamshell design. On-skin sensor assembly 260 may includesimilar components as electronics unit 140 described above in FIG. 1(e.g. a potentiostat, a power source for providing power to sensor 138,signal processing components, data storage components, and acommunication module (e.g., a telemetry module) for one-way or two-waydata communication, a printed circuit board (PCB), an integrated circuit(IC), an Application-Specific Integrated Circuit (ASIC), amicrocontroller, and/or a processor). As shown, the outer housing mayfeature a generally oblong shape. The outer housing may further comprisean sensor assembly aperture 396 disposed substantially through a centerportion of outer housing and adapted for sensor 338 and needle insertionthrough a bottom of on-skin sensor assembly 360. In some embodiments,sensor assembly aperture 396 may be a channel or elongated slot. On-skinsensor assembly 360 may further comprise an adhesive patch 326configured to secure on-skin sensor assembly 360 to skin of the host. Insome embodiments, adhesive patch 326 may comprise an adhesive suitablefor skin adhesion on its underside, for example a pressure sensitiveadhesive (e.g., acrylic, rubber-based, or other suitable type) bonded toa carrier substrate (e.g., spun lace polyester, polyurethane film, orother suitable type) for skin attachment, though any suitable type ofadhesive is also contemplated. In some embodiments, adhesive patch 326may further comprise an adhesive on its topside, e.g., the non-skincontacting side to aid adherence of adhesive patch 326 to a portion ofan associated applicator during manufacture and/or to maintain adhesivepatch 326 in a substantially flat orientation before deployment to theskin of a host. In some embodiments, the adhesive applied to the topsidemay be weaker than the adhesive applied to the underside to ensureappropriate transfer of the on-skin sensor assembly to the skin of thehost. As shown, adhesive patch 396 may feature an aperture 398 alignedwith sensor assembly aperture 396 such that sensor 338 may pass througha bottom of on-skin sensor assembly 360 and through adhesive patch 396.

FIG. 3B illustrates a bottom perspective view of on-skin sensor assembly360 of FIG. 3A. FIG. 3B further illustrates sensor assembly aperture 396disposed substantially in a center portion of a bottom of on-skin sensorassembly 360, and aperture 398, both adapted for sensor 338 and needleinsertion.

FIG. 91 illustrates a perspective view of an on-skin sensor assembly9160, according to some embodiments. On-skin sensor assembly 9160 may besubstantially similar to other on-skin sensor assemblies described inthis application, such as on-skin sensor assemblies 160, 260, and 360.On-skin sensor assembly 9160 may feature an adhesive patch 9126 and aclamshell design comprising a top shell and a bottom shell, similar toon-skin sensor assembly 360. Further, on-skin sensor assembly 9160 mayinclude a plurality of attachment points 9162 a and 9162 b, similar toon-skin sensor assembly 160. On-skin sensor assembly 9160 may include anaperture 9296. Aperture 9296 may be a through-hole extending throughon-skin sensor assembly 9160. Aperture 9296 may be configured to allow aneedle and/or sensor to pass through. In some embodiments, on-skinsensor assembly 9160 may further include an aperture 9294. Aperture 9294may extend from a top surface of on-skin sensor assembly 9150 a certaindepth through on-skin sensor assembly 9160. In some embodiments,aperture 9294 is configured to engage with an anti-rotational featuresuch as base 7152 of needle hub 7150 described in FIG. 78.

In some embodiments, on-skin sensor assembly 9160 includes anidentification tag 9150. Identification tag 9150 may be located on a topsurface of on-skin sensor assembly 9150 (as shown), or on a side surfaceof on-skin sensor assembly. Identification tag 9150 may be an imagewhich resembles a logo or mark identifying the manufacturer of theon-skin sensor assembly. Additionally, identification tag 9150 may beconfigured to be scanned by a user to pair the on-skin sensor assemblywith a device, such as handheld device 112. In some embodiments,identification tag 9150 is a code such as, but not limited to, a QRcode, a matrix code, a 2-D barcode, or a 3-D barcode. The code may beimbedded in the image of identification tag 9150.

FIG. 4 illustrates a cross-sectional view of on-skin sensor assembly 360of FIGS. 3A and 3B. FIG. 4 illustrates the first, top portion 392 andthe second, bottom portion 394 of the outer housing, adhesive patch 326,sensor assembly aperture 396 in the center portion of on-skin sensorassembly 360, aperture 398 in the center portion of adhesive patch 326,and sensor 338 passing through sensor assembly aperture 396. Theelectronics unit, previously described in connection with FIG. 3A, mayfurther include a circuit board 404 and a battery 402 configured toprovide power to at least circuit board 404.

FIG. 87 illustrates a cross-sectional view of on-skin sensor assembly360 of FIGS. 3A, 3B and 4, further comprising an upper patch 328,according to some embodiments. Upper patch 328 may comprise an adhesivesuitable for skin adhesion, device adhesion, or a combination thereof,on its underside, for example a pressure sensitive adhesive (e.g.,acrylic, rubber-based, or other suitable type) bonded to a carriersubstrate (e.g., spun lace polyester, polyurethane film, or othersuitable type) for skin and/or device attachment, though any suitabletype of adhesive is also contemplated. In some embodiments, such anadhesive may be the same as the adhesive applied to the underside ofpatch 326. In some other embodiments, the adhesive may be different fromthe adhesive applied to the underside of patch 326. In some embodiments,upper patch 328 may be shaped as a circle, oval, partial strip, as an X,or as any other shape or form suitable for securing upper patch 328 tolower patch 326 and/or the skin of the host. The upper patch 328 mayfully or partially cover on-skin sensor assembly 360. The upper patch328 may improve adhesion lifespan of on-skin sensor assembly 360 on skin130 of the host by adding additional adhesive contact area to thesurface of the skin 130 and/or providing a single surface covering thewearable that reduces the risk of inadvertent mechanical removal (e.g.catching, snagging, tearing) by reducing catch surfaces/edges on on-skinsensor assembly 360. It is contemplated that reducing surfaces ofon-skin sensor assembly 360 that are substantially perpendicular to thebody surfaces may improve catch resistance. Such increased wearablelifespan provided by upper patch 328 may be a valuable property,especially as systems move toward and beyond 10-14 day wearable adhesionsolutions.

In some embodiments, upper patch 328 may be assembled into anyapplicator in this description, above on-skin sensor assembly 360, withunderside adhesive exposed. Upon deployment of on-skin sensor assembly360 by the applicator, patch 326 may adhere to skin 130 of the host andupper patch 328 may be adhered over on-skin sensor assembly 360 and ontoskin 130 of the host by one or more features of the applicator, forexample, a holder and/or needle carrier assembly as described inconnection with any figure herein.

Applicator Embodiments

FIG. 5 illustrates an exploded perspective view of an applicator 500 forapplying on-skin sensor assembly 160 to skin 130 of a host, according tosome embodiments. In some embodiments, applicator 500 may include anapplicator housing 502 having an opening at its bottom and configured tohouse at least one or more mechanisms utilized to apply on-skin sensorassembly 160 to skin 130 of a host. Applicator housing 502 may be formedof any suitable material, e.g., a polymer, polycarbonate, ABS, nylon,polyethylene, polypropylene, etc. In some embodiments, applicatorhousing 502 may be configured to cover at least one feature ofapplicator housing 502, for example a guide of a reciprocating or backand forth mechanism, e.g., a scotch-yoke mechanism (see FIG. 6B).

Applicator 500 includes an activation element 504 configured to activatea drive assembly of applicator 500. In some embodiments, activationelement 504 may be a button, a switch, a toggle, a slide, a trigger, aknob, a rotating member, a component that deforms and/or flexes or anyother suitable mechanism for activating a drive assembly of applicator500.

Applicator 500 may further comprise a needle carrier assembly 508,including an insertion element (not shown in FIG. 5) configured toinsert sensor 138 of on-skin sensor assembly 160 (e.g., FIG. 1) at leastpartially into skin 130 of the host. The insertion element is furtherillustrated in FIG. 6H as attaching to needle carrier assembly 508 andextending in the distal direction, substantially along an axis ofinsertion. In some embodiments, needle carrier assembly 508 comprises aneedle carrier or shuttle. In some embodiments, the insertion elementcomprises a needle, for example, an open sided-needle, a deflected-tipneedle with a deflected-tip, a curved needle, a polymer-coated needle, ahypodermic needle, or any other suitable type of needle or structure, aswill be described in more detail in connection with at least FIGS. 47-50and 80A-B. In yet other embodiments, insertion element may comprisesensor 138 itself, sufficiently rigid to be inserted partially into skin130 of the host with minimal or no structural support, such as describedin U.S. Pat. No. 9,357,951, which was filed on Sep. 29, 2010, U.S.Patent Publication No. US 2014/0107450, which was filed on Feb. 28,2013, and U.S. Patent Publication No. US 2015/0289788, which was filedon Apr. 10, 2014. The entire contents of U.S. Pat. No. 9,357,951, U.S.Patent Publication No. 2014/0107450, and U.S. Patent Publication No.2015/0289788 are incorporated by reference herein.

Applicator 500 may further comprise a drive assembly 510 configured todrive the insertion element of needle carrier assembly 508 in a distaldirection to a distal insertion position and in a proximal directionfrom the distal insertion position to a proximal retraction position. Adistal direction may be defined as extending towards an open-ended sideof the applicator 500 along a path needle carrier assembly 508 isconfigured to travel. The distal direction may also be defined astowards the skin of a user. A proximal direction may be defined as adirection extending in a substantially opposite direction from thedistal direction. In some embodiments, the distal direction and theproximal direction extend along an insertion axis of the insertionelement and of needle carrier assembly 508.

Drive assembly 510 may include a rotating drive element 514 coupled toneedle carrier assembly 508 via an axle 526. In some embodiments,rotating drive element 514 comprises a cam feature, e.g., a wheel cam,having a substantially circular or ovoid circumference. Rotating driveelement 514 may be configured to rotate with respect to needle carrierassembly 508 about an axis of rotation 518 coincident with a centerlineof axle 526. Rotating drive element 514 may further include a pin 516disposed at a position on a face of rotating drive element 514 displacedradially from axis of rotation 518. Pin 516 is configured to travel in aguide (see FIG. 6B) of applicator housing 502.

Drive assembly 510 may further include a spring 512. Spring 512 may be atorsion spring, a clock spring, a power spring, or any other suitabletype of spring. Spring 512 may be formed of any suitable materialincluding but not limited to plastic or metal, e.g., stainless steel. Insome embodiments, spring 512 is pre-compressed before activation of theapplicator. In some embodiments, spring 512 is configured to beadditionally loaded during activation of the applicator. Spring 512 mayhave a first end 520 coupled to needle carrier assembly 508 and a secondend 522 coupled to rotating drive element 514. Spring 512 may bedisposed coaxially with axle 526. Spring 512 may be configured to, uponactivation of drive assembly 510, rotate rotating drive element 514 in asingle direction with respect to needle carrier assembly 508. In someembodiments, spring 512 is configured, upon activation of drive assembly510, to unwind by rotating greater than zero degrees and less than 360degrees. In some embodiments, spring 512 is pre-wound between 30 and1440 degrees.

By virtue of rotating drive element 514 being configured to rotate withrespect to needle carrier assembly 508, about axis of rotation 518, andpin 516 being restrained to travel in the guide of applicator housing502, rotational motion of rotating drive element 514, driven by spring512, is converted into linear, reciprocating motion of needle carrierassembly 508 along axis 590 and, therefore, of the insertion element(not shown). More specifically, rotation of rotating drive element 514drives insertion element 508 in the distal direction to the distalinsertion position and in the proximal direction from the distalinsertion position to the proximal retraction position. Such embodimentsmay be able to omit handoff mechanisms between aspects of drive assembly510 that separately drive the needle carrier assembly 508 in the distaland proximate directions by virtue of a single mechanism that convertsrotational motion into reciprocating linear motion.

Applicator 500 may further include a holder 524 releasably coupled toneedle carrier assembly 508 and configured to guide on-skin sensorassembly 160 while coupled to needle carrier assembly 508. In someembodiments, holder 524 may also be referred to as a carrier ortransport member.

FIG. 6A-6H illustrates cutaway and perspective views of several featuresof applicator 500 of FIG. 5, according to some embodiments. FIG. 6Aillustrates a cutaway view of applicator 500 including applicatorhousing 502, activation element 504, needle carrier assembly 508,rotating drive element 514, pin 516, and holder 524. Each of thesecomponents may have functionality as previously described in connectionwith at least FIG. 5.

FIG. 6B illustrates guide 582 in applicator housing 502. In someembodiments, guide 582 may comprise a scotch-yoke track in which pin 516is configured to travel upon activation of drive assembly 510, asrotating drive element 514 rotates.

FIG. 6C illustrates a plurality of tracks 622 a, 622 b, 622 c inapplicator housing 502 in which a respective one of a plurality ofprotrusions or ribs 624 a, 624 b, 624 c of needle carrier assembly 508are configured to slide. Accordingly, tracks 622 a-622 c in applicatorhousing 502 define a path of travel for needle carrier assembly 508. Insome embodiments, this path of travel is substantially linear andlongitudinal. Although three tracks and protrusions are shown in FIG.6C, any number of tracks and respective protrusions are contemplated.For ease of understanding, FIG. 6C illustrates a partial bottom view ofapplicator 500, which also shows portions of on-skin sensor assembly 160and holder 524.

FIG. 6D illustrates an embodiment where needle carrier assembly 508comprises a locking element 632 configured to prevent rotating driveelement 514 from rotating. Specifically, rotating drive element 514comprises a protrusion 634 in contact with retention element 632, whichprevents protrusion 634 from traveling in a path it would otherwise takeas spring 512 releases at least a portion of its stored energy inrotating drive element 514. In some embodiments, retention element 632comprises a deflectable tab formed of a material such as a polymer,polycarbonate, ABS, nylon, polyethylene, polypropylene, or any othersuitable material. Activation element 504 comprises a protrusion 640configured to deflect retention element 632 such that protrusion 634 isno longer held by retention element 632, thereby allowing rotating driveelement 514 to rotate and activating drive assembly 510. Rotating driveelement 514 further comprises a ridge 636 configured to limit rotationof rotating drive element 514 as rotating drive element 514 rotates andridge 636 comes in contact with retention element 632.

FIG. 6E illustrates a retention element 642 of holder 524 and a stopelement 644 of applicator housing 502 configured to immobilize holder524 to applicator housing 502 upon needle carrier assembly 508 reachingthe distal insertion position. In some embodiments, retention element642 is a deflectable arm, or any other type of protrusion or snap. Forexample, as needle carrier assembly 508 travels in the distal direction,as a result of spring 512 turning rotating drive element 514, retentionelement 642 slides along an inside surface of applicator housing 502until retention element 642 is slightly deflected by stop element 644,then snapping in an outward direction under stop element 644. At thispoint, needle carrier assembly 508 may be free to progress in theproximal direction as a result of spring 512 further turning rotatingdrive element 514. Stop element 644 will prevent retention element 642,and so holder 524, from traveling in the proximal direction. In thisway, movement of needle carrier assembly 508 in the proximal direction,after reaching the distal insertion position, releases holder 524 fromneedle carrier assembly 508 and/or on-skin sensor assembly 160.

FIG. 6F illustrates a protrusion 652 of holder 524 and a protrusion 654of applicator housing 502 configured to prevent holder 524 fromtravelling beyond the distal insertion position in the distal direction.For example, as holder 524 is driven in the distal direction by needlecarrier assembly 508, protrusion 652 travels along an inside surface ofthe applicator housing 502 until protrusion 652 comes in contact withprotrusion 654, at which point holder 524 is prevented from furthertravel in the distal direction.

FIG. 6G illustrates on-skin sensor assembly 160 including a plurality ofattachment points 662 a-662 f configured to mate with respectiveretention elements on needle carrier assembly 508 and/or holder 524while traveling at least partially toward the distal insertion position,in the distal direction, during applicator activation. In someembodiments, attachment points 662 a-662 f are small grooves orindentations. Although a plurality of attachment points 662 a-662 f areillustrated, any number of attachment points are contemplated. In someembodiments, the respective retention elements may comprise snap fits,friction fits, interference features, elastomeric grips and/or adhesivesconfigured to couple on-skin sensor assembly 160 with needle carrierassembly 508 and/or holder 524.

Moreover, during pressure fluctuations, such as at high altitude orvacuum during sterilization processes for example, air present withinon-skin sensor assembly 160 may exert a deforming force from within thecavity of on-skin sensor assembly 160. Although not shown in FIG. 6G, insome embodiments, on-skin sensor assembly 160 may have at least aportion formed with a reduced thickness or a second material (e.g. anelastomer) and, therefore, reduced strength and rigidity, such that whenapplicator 500 is exposed to such pressure fluctuations, the portionshaving the reduced thickness or second material deform in a controlledmanner, thereby reducing or eliminating damage that would otherwiseoccur to on-skin sensor assembly 160 due to undesirable uncontrolledexpansion of on-skin sensor assembly 160. The portion formed withreduced thickness or a second material may be selected to directcontrolled expansion away from datum and/or retention features securingthe on-skin sensor assembly to applicator assembly. Such a feature maybe present in any applicator described herein.

FIG. 6H illustrates retention elements 672 a, 672 b of holder 528configured to releasably couple on-skin sensor assembly 160 to holder528 as needle carrier assembly 508 travels in the distal direction tothe distal insertion position, and to decouple on-skin sensor assembly160 from holder 528 as needle carrier assembly 508 travels in theproximal direction from the distal insertion position towards theproximal retraction position. Specifically, retention elements 672 a,672 b may each comprise a first end 676 a, 676 b, a second end 678 a,678 b, and a pivot point 680 a, 680 b. As needle carrier assembly 508travels in the distal direction to the distal insertion position, firstend 676 a, 676 b of each of retention elements 672 a, 672 b isimmobilized in a respective guide 674 a, 674 b of needle carrierassembly 508 and each of retention elements 672 a, 672 b is immobilizedagainst interference points 682 a, 682 b of needle carrier assembly 508,thereby releasably coupling second ends 678 a, 678 b to attachmentpoints 662 a, 662 b of on-skin sensor assembly 160. In some embodiments,guides 674 a, 674 b comprise a slot or a stop element. Since retentionelements 642, 644 and/or protrusions 652, 654 immobilize holder 524 atthe distal insertion position (as described in FIG. 6E), as needlecarrier assembly 508 travels back in the proximal direction, needlecarrier assembly 508 separates from holder 524, thereby separating firstends 676 a, 676 b of retention elements 672 a, 672 b from respectiveslots 674 a, 674 b, allowing first ends 676 a, 676 b to deflect inwardand second ends 678 a, 678 b to deflect outward from attachment points662 a, 662 b of on-skin sensor assembly 160 as retention elements 672 a,672 b rotate about pivot points 680 a, 680 b. Although two retentionelements are illustrated, any number of retention elements arecontemplated. Moreover, some alternative mechanisms that may performsuch retention and release actions are further described in connectionwith at least FIGS. 35A-37C below. Any of these alternative mechanismsare contemplated for use with applicator 500.

A brief description of the operation of applicator 500 follows withrespect to FIGS. 7A-7F, which illustrate several perspective views ofthe applicator of FIG. 5 in sequence, during operation, according tosome embodiments.

FIG. 7A illustrates a pre-activated state of applicator 500. Applicatorhousing 502 and slot 582 remain stationary with respect to the skin ofthe host during activation. Activation element 504 is in apre-activation position. Insertion assembly 508 is also in apre-activation position, coupled to holder 524, which is releasablycoupled to on-skin sensor assembly 160, as described in connection withat least FIGS. 6A-6H. At least a portion of insertion element 674 ofneedle carrier assembly 508 is illustrated as protruding, in a distaldirection, below on-skin sensor assembly 160. Insertion element 674 maycomprises a needle, for example, an open sided-needle, a needle with adeflected-tip, a curved needle, a polymer-coated needle, a hypodermicneedle, deflected-tip or any other suitable type of needle or structure,as will be described in more detail in connection with at least FIGS.47-50 and 80A-B. Insertion element 674 may be configured to guide atleast a portion of sensor 138 of on-skin sensor assembly 160. rotatingdrive element 514 of drive assembly 510 is shown in a pre-activationposition, having pin 516 located at a first position within guide 582 ofapplicator housing 502, and having protrusion 634 in contact withretention element 632. In FIG. 7A, pin 516 is positioned approximately30 degrees (illustrated as clockwise, though counterclockwise is alsocontemplated) from a bottom dead center orientation relative to an axisof rotation of rotating drive element 514 that passes through a centerof the face on which pin 516 is disposed.

FIG. 7B illustrates a state of applicator 500 at activation. Activationelement 504 is illustrated in an activated position, having been pushedlongitudinally in the distal direction by a user, for example. In theactivated position, activation element 504 deflects retention element632 such that protrusion 634 of rotating drive element 514 is unimpededfrom moving, thus allowing rotating drive element 514 to rotate by theunwinding of spring 512. Since FIG. 7B illustrates applicator 500 justat activation, rotating drive element 514, pin 516, needle carrierassembly 508, insertion element 674, holder 524 and on-skin sensorassembly 160 are still shown in their pre-activation orientations andlocations as in FIG. 7A. However, rotating drive element 514 will rotatein the direction of the circular arrow, and needle carrier assembly 508,insertion element 674, holder 524 and on-skin sensor assembly 160 willbe driven, by pin 516 under rotating drive element 514 rotation, in thedistal direction to the distal insertion position. However, the presentdisclosure is not so limited, and rotating drive element 514 may beconfigured to rotate in a direction opposite of the direction of thecircular arrow.

FIG. 7C illustrates a state of applicator 500 during activation.Activation element 504 is illustrated in the activated position of FIG.7B. Rotating drive element 514 is shown as having rotated a portion of arevolution, indicated by the circular arrow, protrusion 634 havingadvanced beyond retention element 632. Pin 516 is shown as having movedto a second position within guide 582. This second position is shown asbeing to the left of the first, pre-activation position. Insertionassembly 508, insertion element 674, holder 524 and on-skin sensorassembly 160 are driven in the distal direction toward the distalinsertion position when rotating drive element 514 is rotated by a forcegenerated by spring 512.

FIG. 7D illustrates applicator 500 during activation, in the distalinsertion position. Activation element 504 is illustrated in theactivated position of FIGS. 7B and 7C. Rotating drive element 514 isshown as having rotated clockwise further compared to FIG. 7C, indicatedby the circular arrow, protrusion 634 having advanced yet further beyondretention element 632. Pin 516 is shown as having moved to a thirdposition within guide 582, shown as being to the right of the first,pre-activation position and the second, activation position of FIG. 7C.Insertion assembly 508, insertion element 674, holder 524 and on-skinsensor assembly 160 are driven in the distal direction to the distalinsertion position as rotating drive element 514 is further rotated bythe force generated by spring 512. In this distal insertion position, atleast a portion of insertion element 674 as well as at least a portionof sensor 138 of on-skin sensor assembly 160 may be inserted into skin130 of the host. At this position, retention elements 642, 644 (see FIG.6) may be engaged and protrusions 652 and 654 (see FIG. 6) may be incontact with one another. In FIG. 7D, pin 516 is positionedapproximately 180 degrees (illustrated as clockwise, thoughcounterclockwise is also contemplated) from the bottom dead centerorientation relative to the axis of rotation of rotating drive element514.

FIG. 7E illustrates applicator 500 during activation. Activation element504 is illustrated in the activated position of FIGS. 7B-7D. Rotatingdrive element 514 is shown as having rotated further compared to FIG.7D, indicated by the circular arrow. Pin 516 is shown as having moved toa fourth position within guide 582. This fourth position is shown asbeing to the right of the first through third positions previouslydiscussed. Insertion assembly 508 and insertion element 674 are nowshown as being driven in the proximal direction from the distalinsertion position as rotating drive element 514 is further rotated bythe force generated by spring 512. Since retention elements 642, 644(see FIG. 6) are engaged and protrusions 652 and 654 (see FIG. 6) may bein contact with one another, holder 524 and on-skin sensor assembly 160are shown as separated from needle carrier assembly 508. In the positionshown by FIG. 7E, on-skin sensor assembly 160 may also be decoupled fromholder 524, as previously described in connection with FIG. 6H.

FIG. 7F illustrates applicator 500 post-activation. Activation element504 is illustrated in the activated position of FIGS. 7B-7E. Rotatingdrive element 514 is shown as having rotated further compared to FIG.7E, indicated by the circular arrow, such that ridge 636 is in contactwith retention element 632, thereby restricting further rotation ofrotating drive element 514. Pin 516 is shown as having moved to a fifthposition within guide 582, which is shown as being to the left of thefourth, right-most position, as pin 516 travels back along guide 582.Insertion assembly 508 and insertion element 674 are shown in theproximal retraction position. Holder 524 and on-skin sensor assembly 160are shown as separated from needle carrier assembly 508. In the positionshown by FIG. 7F, on-skin sensor assembly 160 may also be decoupled fromholder 524, as previously described in connection with FIG. 6H. In FIG.7F, pin 516 is positioned approximately 330 degrees (illustrated asclockwise, though counterclockwise is also contemplated) from the bottomcenter orientation relative to the axis of rotation of rotating driveelement 514.

FIGS. 8-10 illustrate cutaway views of applicators 800, 900, 1000similar to applicator 500 of FIG. 5, however, alternatively havingactivation elements 804, 904, 1004 disposed on an upper, medial, andlower side of, rather than on a top of, an applicator housing 802, 902,1002, respectively. Applicators 800, 900, 1000 may comprisesubstantially all features of applicator 500 and have substantially thesame operation. For example, applicator housing 802, 902, 1002,activation element 804, 904, 1004, a needle carrier assembly 808, 908,1008, a rotating drive element 814, 914, 1014, including a pin 816, 916,1016 and a protrusion 834, 934, 1034 and a retention element 832, 932,1032 may correspond substantially to applicator housing 502, activationelement 504, needle carrier assembly 508, rotating drive element 514including pin 516 and protrusion 504, and retention element 502 ofapplicator 500, respectively.

However, in FIG. 8, activation element 804 is disposed on an upper side,rather than on a top, of applicator housing 802 and may be configuredto, upon activation, deflect retention element 832 such that protrusion834 no longer restrains rotating drive element 814 from rotating underforce of a spring (not shown in FIG. 8) similar to spring 512 ofapplicator 500. In FIG. 9, activation element 904 is disposed on amedial side, rather than on a top, of applicator housing 902 and may beconfigured to, upon activation, deflect retention element 932 such thatprotrusion 934 no longer restrains rotating drive element 914 fromrotating under force of a spring (not shown in FIG. 9) similar to spring512 of applicator 500. As shown, due to the medial side location ofactivation element 904, retention element 932 may be locatedsubstantially on a side of rotating drive element 914.

In FIG. 10, activation element 1004 is disposed on a lower side, ratherthan on a top, of applicator housing 1002 and may be configured to, uponactivation, deflect retention element 1032 such that protrusion 1034 nolonger restrains rotating drive element 1014 from rotating under forceof a spring (not shown in FIG. 10) similar to spring 512 of applicator500. As shown, due to the lower side location of activation element1004, retention element 1032 may be located substantially on a side ofrotating drive element 1014. 50

An example of steps for assembling an applicator such as applicators500, 800, 900, 1000 of FIGS. 5 and 8-10 will now be discussed inconnection with FIGS. 11A-11H.

FIG. 11A illustrates coupling first end 520 of spring 512 to needlecarrier assembly 508. First end 520 may be coupled to, or disposedagainst, a protrusion 1102 of needle carrier assembly 508 and spring 512may be inserted around a hub 1104 of needle carrier assembly 508 suchthat spring 512 and hub 1104 are disposed coaxially with one another.

FIG. 11B illustrates coupling second end 522 of spring 512 with rotatingdrive element 514 and inserting axle 526 into hub 1104 of needle carrierassembly 508 within which axle 526 may rotate. Axle 526, hub 1104, andspring 512 may be disposed coaxially with respect to one another. Asshown by the circular arrow, rotating drive element 514 may be rotatedabout axle 526 in a circular direction opposite of a direction thatrotating drive element 514 rotates during activation, therebypre-storing energy in spring 512. Axle 524 may be fully inserted intothe portion of needle carrier assembly 508 such that protrusion 634 isin contact with retention element 632, thereby preventing rotating driveelement 514 from rotating until activation. In some embodiments,rotating drive element 514 may be rotated about axle 504 such thatspring 512 is only partially wound. In such embodiments, spring 512 maybe fully wound at a later stage of assembly. Although FIG. 11Billustrates rotating drive element 514 as having a male-type aspectconfigured to mate with a female-type aspect of hub 1104, the presentdisclosure also contemplates rotating drive element 514 as having afemale-type aspect configured to mate with a male-type aspect of hub1104.

FIG. 11C illustrates pushing retention elements 672 a, 672 b toward acenter of holder 524 and coupling holder 524 to needle carrier assembly508 by seating first ends 676 a, 676 b of retention elements 672 a, 672b into respective slots 674 a, 674 b of needle carrier assembly 508.

FIG. 11D illustrates coupling on-skin sensor assembly 160 to holder 524by snapping second ends 678 a, 678 b (not shown in FIG. 11D) ofretention elements 672 a, 672 b into attachment points 662 a, 662 b ofon-skin sensor assembly 160. In some embodiments, retention elements 672a, 672 b may comprise snap fits, friction fits, interference features,elastomeric grips and/or adhesives.

FIG. 11E illustrates inserting the assembled needle carrier assembly508, rotating drive element 514, holder 524, and on-skin sensor assembly160 into applicator housing 502 through the opening in the bottom ofapplicator housing 502 and through a vertical portion of guide 582 (seeFIG. 11F). During such insertion, pin 516 of rotating drive element 514is inserted along at least the vertical portion of guide 582 inapplicator housing 502, as shown in FIG. 11F. Accordingly, spring 512(not shown in FIGS. 11E, 11F) may not be fully wound at this point,instead being partially wound to the extent that pin 516 of rotatingdrive element 514 is positioned to be inserted along guide 582 inapplicator housing 502.

FIG. 11G illustrates positioning the assembled needle carrier assembly508, rotating drive element 514, holder 524, and on-skin sensor assembly160 further in the proximal direction into applicator housing 502 suchthat pin 516 of rotating drive element 514 follows guide 582 ofapplicator housing 502, thereby turning rotating drive element 514 fullywinding spring 512 (not shown in FIG. 11G) and positioning protrusion634 in contact with retention element 632 such that the drive assembly,comprising at least rotating drive element 514, having pin 516, andspring 512, are loaded for activation.

FIG. 11H illustrates a magnified cutaway view of area 1106 of FIG. 11Gillustrating the relationship between rotating drive element 514, pin516, guide 582, protrusion 634 and retention element 632.

FIG. 11J illustrates inserting activation element 504 into applicatorhousing 502.

FIG. 12 illustrates an exploded perspective view of another applicator1200 for applying an on-skin sensor assembly to a skin of a host,according to some embodiments. Applicator 1200 may include an applicatorhousing 1202 having an opening in its bottom and configured to house atleast one or more mechanisms utilized to apply on-skin sensor assembly160 to skin 130 (see FIG. 2) of a host.

Applicator 1200 includes an activation element 1204 configured toactivate a drive assembly of applicator 1200. In some embodiments,activation element 1204 may be a button, a switch, a toggle, a slide, atrigger, a knob, a rotating member, a component that deforms and/orflexes or any other suitable mechanism for activating a drive assemblyof applicator 1200. Applicator 1200 may further comprise a needlecarrier assembly 1208, including an insertion element (not shown in FIG.12) configured to insert sensor 138 of on-skin sensor assembly 160(e.g., FIG. 1) into skin 130 of the host. In some embodiments, theinsertion element comprises a needle, for example a C-needle, as will bedescribed in more detail in connection with at least FIGS. 47-50 and80A-B.

Applicator 1200 may further comprise a drive assembly 1210 configured todrive the insertion element of needle carrier assembly 1208 in thedistal direction to a distal insertion position and in the proximaldirection from the distal insertion position to a proximal retractionposition. A distal direction may be defined as extending towards anopen-ended side of the applicator 1200 along a path needle carrierassembly 1208 is configured to travel. The distal direction may also bedefined as towards the skin of a user. A proximal direction may bedefined as a direction extending in a substantially opposite directionfrom the distal direction. In some embodiments, the distal direction andthe proximal direction extend along an insertion axis of the insertionelement and of needle carrier assembly 1208.

Drive assembly 1210 may include a spring 1212 having a first tang 1220(e.g., end) and a second tang 1222 (e.g., end). Spring 1212 may be atorsion spring, a double torsion spring, or any other suitable type ofspring. Spring 1212 may be supported by a spring spool 1250 comprising afirst portion 1250 a and an optional second portion 1250 b. In someembodiments, spring 1212 is self-supporting and is not supported by aspring spool. First portion 1250 a may be configured to couple withsecond portion 1250 b such that spring spool 1250 is disposed coaxiallywith spring 1212 and provides support for spring 1212 along an axis ofrotation 1218 of spring 1212. As will be shown in more detail inconnection with FIG. 13, first tang 1220 of spring 1212 may be coupledto applicator housing 1202, e.g., to a hook or protrusion of applicatorhousing 1202. Second tang 1222 may be coupled to needle carrier assembly1208, e.g., a hook or protrusion of needle carrier assembly 1208. Uponactivation of drive assembly 1210, first tang 1220 and second tang 1222of spring 1212 unwind in opposite clockwise or counterclockwisedirections, thereby driving spring 1212 in an arc and insertion element1208 in the distal direction to the distal insertion position and in theproximal direction from the distal insertion position. The arc throughwhich drive assembly 1210 travels may extend in a directionapproximately perpendicular to the distal direction and the proximaldirection, or in an arc defined by the tangs of the spring and therotation points.

Applicator 1200 may further include a holder 1224 releasably coupled toneedle carrier assembly 1208 and configured to guide on-skin sensorassembly 160 while coupled to needle carrier assembly 1208. In someembodiments, holder 1224 may comprise a stripper plate. As will bedescribed in more detail below, on-skin sensor assembly 160 may bestripped from holder 1224 and needle carrier assembly 1208 once on-skinsensor assembly 160 is disposed on skin 130 of the host.

FIG. 13A-13F illustrate perspective and cutaway views of severalfeatures of applicator 1200 of FIG. 12, according to some embodiments.FIG. 13A illustrates a cross-sectional view of applicator 1200,including applicator housing 1202 having retention element 1334,activation element 1204, spring spool 1250, spring 1212 having firsttang 1220 and second tang 1222, needle carrier assembly 1208 havingretention element 1332, holder 1224, and on-skin sensor assembly 160. Insome embodiments, retention element 1332 may comprise snap fits,friction fits, interference features, elastomeric grips and/or adhesivesconfigured to couple on-skin sensor assembly 160 with needle carrierassembly 1208 and/or holder 1224. Each of these components may havefunctionality as previously described in connection with at least FIG.12. Moreover, first tang 1220 is configured to, upon activation of thedrive assembly, rotate about a rotation point 1336. Second tang 1222 issimilarly configured.

FIG. 13F illustrates a magnified perspective view of a retention element1342 of holder 1224 and a stop element 1344 of applicator housing 1202configured to immobilize holder 1228 to applicator housing 1202 uponneedle carrier assembly 1208 reaching the distal insertion position. Insome embodiments, retention element 1342 is a deflectable arm. Forexample, as needle carrier assembly 1208 travels in the distaldirection, as a result of spring 1212 partially unwinding, retentionelement 1342 slides along an inside surface of applicator housing 1202and is deflected by stop element 1344 until retention element 1342 snapsunder stop element 1344. In some embodiments, the functionality betweenretention element 1342 and stop element 1344 may be swapped, e.g., stopelement 1344 may be configured to be deflected by and snap overretention element 1342. At this point, though needle carrier assembly1208 may be free to progress in the proximal direction, as a result ofspring 1212 unwinding further, stop element 1344 will prevent retentionelement 1342, and so holder 1224, from traveling back in the proximaldirection. In this way, movement of needle carrier assembly 1208 in theproximal direction after reaching the distal insertion position allowsholder 1224 and/or needle carrier assembly 1208 to be released fromon-skin sensor assembly 160.

FIG. 13B illustrates a magnified cutaway view of a portion of needlecarrier assembly 1208 comprising a retention element 1332 configured tointerlock with a retention element 1334 of applicator housing 1202 andprevent needle carrier assembly 1208 from separating from applicatorhousing 1202 in the loaded, pre-activated position. Activation element1204 is configured to deflect retention element 1332 such that retentionelement 1334 no longer holds retention element 1332, thereby allowingspring 1212 to separate needle carrier assembly 1208 from applicatorhousing 1202 and activating drive assembly 1210.

FIG. 13C illustrates a magnified view of second tang 1222 of a springcoupled to needle carrier assembly 1208, for example, via a hook 1348configured to immobilize second tang 1222 to needle carrier assembly1208. The fastening concept described for second tang 1222 in FIG. 13Cmay also be utilized for first tang 1220.

FIG. 13D illustrates on-skin sensor assembly 160 including a pluralityof attachment points 662 a-662 c configured to mate with respectiveretention elements 1372 a-1372 c on needle carrier assembly 1208 and/orholder 1224 while traveling in the distal direction at least partiallytoward the distal insertion position during applicator activation. Insome embodiments, where holder 1224 comprises a stripper plate, holder1224 may function similarly to a stripper plate in punch and diemanufacturing or injection molding processes. Although a plurality ofattachment points 662 a-662 c are illustrated, any number of attachmentpoints are contemplated. In some embodiments, retention elements 1372a-1372 c may comprise snap fits, friction fits, interference features,elastomeric grips and/or adhesives.

Retention elements 1372 a-1372 c of needle carrier assembly 1208 and/orholder 1224 are configured to releasably couple on-skin sensor assembly160 to holder 1228 as needle carrier assembly 1208 travels in the distaldirection to the distal insertion position, and to decouple on-skinsensor assembly 160 from needle carrier assembly 1208 and/or holder 1228as needle carrier assembly 1208 travels in the proximal direction fromthe distal insertion position towards the proximal retraction position.Specifically, since retention elements 1342, 1344 immobilize holder 1224from traveling in the proximal direction at the distal insertionposition, as needle carrier assembly 1208 travels back in the proximaldirection. This causes needle carrier assembly 1208 to separate fromholder 1224 and on-skin sensor assembly 160, thereby decouplingretention elements 1372 a-1372 c from attachment points 662 a-662 c ofon-skin sensor assembly 160. Although two retention elements areillustrated, any number of retention elements are contemplated.Moreover, alternative mechanisms that may perform such retention andrelease actions are further described in connection with at least FIGS.35A-37C below. Any of these alternative mechanisms are contemplated foruse with applicator 1200.

FIG. 13E illustrates a perspective view of a plurality of tracks 1322 a,1322 b, 1322 c in applicator housing 1202 in which a respectiveplurality of protrusions 1324 a, 1324 b, 1324 c of needle carrierassembly 1208 are configured to slide. Accordingly, tracks 1322 a-1322 cin applicator housing 1202 define a path of travel for needle carrierassembly 1208. In some embodiments, this path of travel is substantiallylinear and longitudinal. Although three tracks and protrusions are shownin FIG. 13E, a single track or a plurality of tracks and respectiveprotrusions are contemplated.

A brief description of the operation of applicator 1200 follows withrespect to FIGS. 14A-14E, which illustrate several cross-sectional viewsof the applicator of FIG. 12 during operation, according to someembodiments.

FIG. 14A illustrates a state of applicator 1200 at activation.Activation element 1204 is illustrated in an activated position, havingbeen pushed longitudinally in the distal direction by a user, forexample. In the activated position, activation element 1204 deflectsretention element 1332 such that retention element 1334 of applicatorhousing 1202 does not prevent needle carrier assembly 1208 from movingwhen spring 1212 unwinds from a pre-wound state. Since FIG. 14Aillustrates applicator 1200 just at activation, spring 1212, needlecarrier assembly 1208, holder 1224 and on-skin sensor assembly 160 areshown in their pre-activation orientations and locations. However,spring 1212 will unwind partially and needle carrier assembly 1208,holder 1224 and on-skin sensor assembly 160 will be driven, by suchunwinding, in the distal direction to the distal insertion position.

FIG. 14B illustrates a state of applicator 1200 during activation.Activation element 1204 is illustrated in the activated position of FIG.14A. Spring 1212 has partially unwound such that first tang 1220 unwindsin a first arc-direction and second tang 1222 unwinds in a secondarc-direction opposite of the first arc-direction. Spring 1212 travelsthrough an arc-direction approximately perpendicular to the distaldirection and the proximal direction, or in an arc defined by the tangsof spring 1212 and their associated rotation points. As a result, needlecarrier assembly 1208, insertion element 1374, holder 1224 and on-skinsensor assembly 160 are driven in the distal direction toward the distalinsertion position by a force generated by spring 1212.

FIG. 14C illustrates applicator 1200 during activation, in a distalinsertion position. Activation element 1204 is illustrated in theactivated position of FIGS. 14A and 14B. Spring 1212 has unwoundfurther, relative to its position as illustrated in FIGS. 14A and 14B,substantially in the direction of the horizontal arrow. Insertionassembly 1208, holder 1224 and on-skin sensor assembly 160 are driven inthe distal direction to the distal insertion position by the forcegenerated by spring 1212. In this distal insertion position, at least aportion of an insertion element coupled to needle carrier assembly 1208similarly to that shown in FIG. 6 (not shown in FIGS. 14A-14E) as wellas at least a portion of sensor 138 of on-skin sensor assembly 160(e.g., FIG. 1) may be inserted into skin 130 of the host. At thisposition, although not shown, retention elements 1342, 1344 (see FIG.13) may be engaged with one another.

FIG. 14D illustrates applicator 1200 during activation. Activationelement 1204 is illustrated in the activated position of FIGS. 14A-14C.Spring 1212 has further unwound and travelled in substantially the samedirection as shown by the arrow. Where unwinding of spring 1212 in FIGS.14A-14C caused movement of the needle carrier assembly 1208 in thedistal direction, because spring 1212 is now on an opposite side of thepoints at which the first tang 1220 and the second tang 1222 areanchored, further unwinding of spring 1212 results in movement of theneedle carrier assembly 1208 in the proximal direction toward theproximal retraction position. Since the retention elements (see FIG. 13)are engaged, holder 1224 and on-skin sensor assembly 160 are shown asseparated from needle carrier assembly 1208. In the position shown byFIG. 14D, on-skin sensor assembly 160 may also be decoupled from holder1224, as previously described in connection with call-out 1330 of FIG.13.

FIG. 14E illustrates applicator 1200 post-activation. Activation element1204 is illustrated in the activated position of FIGS. 14A-14D. Spring1212 is illustrated as having unwound further compared to its positionas illustrated in FIG. 14D and having travelled substantially in thedirection indicated by the arrow. Insertion assembly 1208 has travelledin the proximal direction indicated by the vertical arrow to theproximal retraction position. Holder 1224 and on-skin sensor assembly160 are shown as separated from needle carrier assembly 1208.

FIGS. 15-17 illustrate perspective views of several exemplary doubletorsional springs that support different configurations of applicator1200, according to some embodiments. Accordingly, any of the springsdescribed by FIGS. 15-17 may be utilized for spring 1212 previouslydiscussed in connection with FIGS. 12-14E. As shown in FIGS. 15-17,different shaped and/or sized cross-bridges 1522 c, 1622 c, 1722 c ofsprings 1512, 1612, 1712 may be provided by flaring one or more tangs ina particular direction.

For example, FIGS. 15-17 illustrate double torsional springs 1512, 1612,1712, each comprising a first winding 1512 a, 1612 a, 1712 a and asecond winding 1512 b, 1612 b, 1712 b. Double torsional springs 1512,1612, 1712 may be formed from a single segment of suitable material,e.g., metal or plastic. First windings 1512 a, 1612 a, 1712 a eachcomprise a first tang 1520 a, 1620 a, 1720 a and a second tang 1522 a,1622 a, 1722 a. Second windings 1512 b, 1612 b, 1712 b each comprise afirst tang 1520 b, 1620 b, 1720 b and a second tang 1522 b, 1622 b, 1722b. For each spring 1512, 1612, 1712, second tangs 1522 a, 1522 b; 1622a, 1622 b; 1722 a, 1722 b may be coupled to one another by across-bridge 1522 c, 1622 c, 1722 c. Cross-bridge 1522 c of FIG. 15 mayhave a length substantially equal to a spacing 1530 between firstwinding 1512 a and second winding 1512 b defined by the extension ofsecond tangs 1522 a, 1522 b from first winding 1512 a and second winding1512 b, respectively. Cross-bridge 1622 c of FIG. 16 may have a lengthexceeding a spacing 1630 between first winding 1612 a and second winding1612 b defined by the extension of second tangs 1622 a, 1622 b fromfirst winding 1612 a and second winding 1612 b, respectively, due tosecond tang 1622 b of second winding 1612 b being flared toward firsttang 1620 b of second winding 1612 b. Cross-bridge 1722 c of FIG. 17 mayhave a length exceeding a spacing 1730 between first winding 1712 a andsecond winding 1712 b defined by the extension of second tangs 1722 a,1722 b from first winding 1712 a and second winding 1712 b,respectively, due to second tang 1722 a of first winding 1712 a beingflared toward first tang 1720 a of first winding 1712 a and second tang1722 b of second winding 1712 b being flared toward first tang 1720 b ofsecond winding 1712 b to provide the increased length of cross-bridge1722 c compared to either cross-bridge 1522 c shown in FIG. 15 orcross-bridge 1622 c shown in of FIG. 16.

FIGS. 18-23 illustrate alternative drive assemblies for utilization inapplicators, such as applicator 1200 of FIG. 12, according to someembodiments. FIG. 18 illustrates a drive assembly comprising a linkageelement 1850. In some embodiments, linkage element 1850 may comprise aflex linkage. The flex linkage may contain one or more living hinge(s).In other embodiments, linkage element 1850 may comprise at least twodiscrete sections configured to pivot about a hinge coupling the atleast two discrete sections.

A flex linkage is a type of hinge assembly formed from an extension of aparent material (e.g., polypropylene plastic). The hinge flex linkage isa thin section of the parent material that acts as a bending connectionwith two larger sections of the parent material. Typically, the largersections of the parent material as well as the hinge will be made of onecontinuous piece of the parent material. Since it is relatively thin andtypically made from flexible materials, the flex linkage is also able torotate about one axis by 180 degrees or more—potentially for manythousands or even millions of cycles. Contrary to most hinges, whichinvolve multiple parts assembled in a traditional pivoting mechanism,flex linkages are not a separate entity. They may be described as apurposeful fault line at a predetermined point in the material which isdesigned such that it does not fail after repeated bending.

Linkage element 1850 has a first end 1852 coupled to an applicatorhousing 1802, a second end 1854 coupled to a needle carrier assembly1808, and a hinge 1856 disposed between first end 1852 and second end1854.

The drive assembly further comprises a spring 1812, which in someembodiments may be a single or double torsion spring. Spring 1812comprises a first tang 1820 coupled to applicator housing 1802 and/or tolinkage element 1850 at first end 1852 or at a position between firstend 1852 and hinge 1856. Spring 1812 further comprises a second tang1822 coupled to needle carrier assembly 1808 and/or to linkage element1850 at second end 1854 or at a position between second end 1854 andhinge 1856. In some embodiments, hinge 1856 may be aligned with an axisof rotation 1818 of spring 1812 to provide smooth operation as well asto reduce any stresses caused by incompatible movement between linkageelement 1850 and spring 1812.

Applicator 1200, utilizing drive assembly 1810, may functionsubstantially as described for applicator 1200 of FIG. 12, however,further including that first end 1852, second end 1854 and hinge 1856 oflinkage element 150 move substantially in alignment with first tang1820, second tang 1822 and axis of rotation 1818 of spring 1812,respectively, during activation.

FIG. 19 illustrates another drive assembly comprising a linkage element1950. Linkage element 1950 has a first end 1952 coupled to an applicatorhousing 1902, a second end 1954 coupled to a needle carrier assembly1908, and a hinge 1956 disposed between first end 1952 and second end1954. The drive assembly further comprises a spring 1912, which in someembodiments may be a single or double torsion spring. Spring 1912comprises a first tang 1920 coupled to linkage element 1950 betweensecond end 1954 and hinge 1956. Spring 1912 further comprises a secondtang 1922 coupled to needle carrier assembly 1908. Upon activation,spring 1912 unwinds and first tang 1952 sweeps an arc while second tang1954 is held substantially stationary against needle carrier assembly1908. As first tang 1952 sweeps its arc, first tang 1952 drives linkageelement 1950 from the bent position shown, hinge 1956 pivoting, untillinkage element 1950 is substantially vertical, and then continuingpivoting until linkage element 1950 is in a substantially mirrororientation from that shown in FIG. 19. This motion drives needlecarrier assembly 1908 in the distal direction, reaching the distalinsertion position when linkage element 1950 is substantially vertical,and then increasingly in the proximal direction as linkage element 1950is further driven from the substantially vertical orientation to thesubstantially mirrored orientation to that shown in FIG. 19.

FIG. 20 illustrates another drive assembly comprising a linkage element2050. Linkage element 2050 has a first end 2052 coupled to an applicatorhousing 2002, a second end 2054 coupled to a needle carrier assembly2008, and a hinge 2056 disposed between first end 2052 and second end2054. The drive assembly further comprises a spring 2012, which in someembodiments may be a single or double torsion spring. Spring 2012comprises a first tang 2020 coupled to linkage element 2050 betweenfirst end 2052 and hinge 2056. Spring 2012 further comprises a secondtang 2022 coupled to applicator body 2002. Upon activation, spring 2012unwinds and first tang 2052 sweeps an arc while second tang 2054 is heldsubstantially stationary against applicator body 2002. As first tang2052 sweeps its arc, first tang 2052 drives linkage element 2050 fromthe bent position shown, hinge 2056 pivoting, until linkage element 2050is substantially vertical, and then continuing pivoting until linkageelement 2050 is in a substantially mirror orientation from that shown inFIG. 20. This motion drives needle carrier assembly 2008 in the distaldirection, reaching the distal insertion position when linkage element2050 is substantially vertical, and then increasingly in the proximaldirection as linkage element 2050 is further driven from thesubstantially vertical orientation to the substantially mirroredorientation to that shown in FIG. 20.

FIG. 21 illustrates another drive assembly comprising a linkage element2150. Linkage element 2150 has a first end 2152 coupled to an applicatorhousing 2102, a second end 2154 coupled to a needle carrier assembly2108, and a hinge 2156 disposed between first end 2152 and second end2154. The drive assembly further comprises a spring 2112, which in someembodiments may be an extension spring. A compression spring is alsocontemplated. However, a compression spring may be coupled between hinge2156 and the closer side of applicator housing 2102. Spring 2112comprises a first end 2120 coupled to linkage element 2150 and a secondend 2122 coupled to applicator body 2102. In some embodiments, first end2120 is coupled to linkage element 2150 between first end 2152 and hinge2156. In other embodiments first end 2120 is coupled to linkage element2150 at hinge 2156. In yet other embodiments first end 2120 is coupledto linkage element 2150 between hinge 2156 and second end 2154. Uponactivation, spring 2112 unwinds through an arc that extends in adirection approximately perpendicular to the distal direction and theproximal direction, or in an arc defined by the tangs of the spring andtheir respective rotation points, driving linkage element 2150 from thebent position shown, hinge 2156 pivoting, until linkage element 2150 issubstantially vertical, and then continuing pivoting until linkageelement 2150 is in a substantially mirror orientation from that shown inFIG. 21. This motion drives needle carrier assembly 2108 in the distaldirection, reaching the distal insertion position when linkage element2150 is substantially vertical, and then increasingly in the proximaldirection as linkage element 2150 is further driven from thesubstantially vertical orientation to the substantially mirroredorientation to that shown in FIG. 21.

FIG. 22 illustrates another drive assembly comprising a leaf spring2212. Leaf spring 2212 comprises a first end 2220 coupled to anapplicator housing 2202 and a second end 2222 coupled to a needlecarrier assembly 2208. Upon activation, leaf spring 2212 unloads in adirection substantially parallel to the axis of insertion, drivingneedle carrier assembly 2208 to the distal insertion position when leafspring 2212 is unloaded.

FIG. 23 illustrates another drive assembly comprising a linkage element2350. Drive assembly 2310 is substantially the same as drive assembly1910 except replacing torsion spring 1912 with leaf spring 2312. Linkageelement 2350 has a first end 2352 coupled to an applicator housing 2302,a second end 2354 coupled to a needle carrier assembly 2308, and a hinge2356 disposed between first end 2352 and second end 2354. The riveassembly further comprises leaf spring 2312 having a first end 2320coupled to linkage element 2350 between second end 2354 and hinge 2356,and a second end 2322 coupled to needle carrier assembly 2308. Uponactivation, spring 2312 unloads and first end 2320 sweeps an arc whilesecond end 2322 is held substantially stationary against needle carrierassembly 2308. As first end 2320 sweeps its arc, first end 2320 driveslinkage element 2350 from the bent position shown, hinge 2356 pivoting,until linkage element 2350 is substantially vertical, and thencontinuing pivoting until linkage element 2350 is in a substantiallymirror orientation from that shown in FIG. 23. This motion drives needlecarrier assembly 2308 in the distal direction, reaching the distalinsertion position when linkage element 2350 is substantially vertical,and then increasingly in the proximal direction as linkage element 2350is further driven from the substantially vertical orientation to thesubstantially mirrored orientation to that shown in FIG. 23.

An example of steps for assembling an applicator such as applicator 1200of FIG. 12 will now be discussed in connection with FIGS. 24A-24M. Tothe extent any step is compatible, the assembly steps of FIGS. 24A-24Mmay also apply to any applicator utilizing the drive assembliesdescribed in connection with FIGS. 18-23.

FIG. 24A illustrates coupling first portion 1250 a and second portion1250 b of spring spool 1250 together inside the windings of spring 1212.FIG. 24B illustrates the assembled spring spool 1250 and spring 1212.Spring spool 1250 and spring 1212 are disposed coaxially with oneanother. FIG. 24C illustrates spring 1212 before winding in thedirection indicated by the circular arrow, having first tang 1220 andsecond tang 1222 in the illustrated positions. FIG. 24D illustratesspring 1212 after winding, having first tang 1220 and second tang 1222in the illustrated positions.

FIG. 24E illustrates coupling wound spring 1212 to needle carrierassembly 1208. In some embodiments, this includes coupling first tang1220 to a hook 1348 of needle carrier assembly 1208 and coupling secondtang 1222 to or disposing second tang 1222 against needle carrierassembly 1208. FIG. 24F illustrates a side view of wound spring 1212coupled to needle carrier assembly 1208, while FIG. 24G illustrates aperspective view of the arrangement shown in FIG. 24F.

FIG. 24H illustrates coupling holder 1224 to needle carrier assembly1208 and on-skin sensor assembly 160 to holder 1224. FIG. 24Jillustrates a side view of on-skin sensor assembly 160, holder 1224, andneedle carrier assembly 1208 assembled, while FIG. 24K illustrates aperspective view of the arrangement shown in FIG. 24J.

FIG. 24L illustrates assembling the complex including on-skin sensorassembly 160, holder 1224, needle carrier assembly 1208, and spring 1212into applicator housing 1202 through the opening in the bottom ofapplicator housing 1202, and insertion of activation element 1204 intoapplicator housing 1202. FIG. 24M illustrates the result of the assemblyshown in FIG. 24L.

FIG. 25 illustrates an exploded perspective view of yet anotherapplicator 2500 for on-skin sensor assembly 160 of an analyte sensorsystem, according to some embodiments. Applicator 2500 may include anapplicator housing 2502 configured to house one or more mechanisms forapplying on-skin sensor assembly 160 to skin 130 of a host. Applicatorhousing 2502 may be formed of any suitable material, e.g., a polymer,polycarbonate, ABS, nylon, polyethylene, polypropylene, etc.

Applicator 2500 includes an activation element 2504 configured toactivate a drive assembly of applicator 2500. In some embodiments,activation element 2504 may be a button, a switch, a toggle, a slide, atrigger, a knob, a rotating member, a component that deforms and/orflexes or any other suitable mechanism for activating a drive assemblyof applicator 2500.Applicator 2500 may further comprise a needle carrierassembly 2508, including an insertion element 2574 configured to insertsensor 138 (e.g., FIG. 1) of on-skin sensor assembly 160 (e.g., FIG. 1)into skin 130 (e.g., FIG. 1) of the host. In some embodiments, insertionelement 2574 comprises a needle, for example, an open sided-needle, aneedle with a deflected-tip, a curved needle, a polymer-coated needle, ahypodermic needle, or any other suitable type of needle or structure, aswill be described in more detail in connection with at least FIGS. 47-50and 80A-B. In yet other embodiments, insertion element may comprisesensor 138, sufficiently rigid to be inserted partially into skin 130 ofthe host with minimal or no structural support.

Applicator 2500 may further comprise a drive assembly 2510 configured todrive insertion element 2574 of needle carrier assembly 2508 in a distaldirection to a distal insertion position and in a proximal directionfrom the distal insertion position to a proximal retraction position.

Applicator 2500 may further include a holder 2524 releasably coupled toneedle carrier assembly 2508 and configured to guide on-skin sensorassembly 160 while coupled to needle carrier assembly 2508. As will bedescribed in more detail below, on-skin sensor assembly 160 may bestripped from holder 2524 and needle carrier assembly 2508 once on-skinsensor assembly 160 is disposed on skin 130 of the host.

Drive assembly 2510 may include a spring 2512, which may be any suitabletype of spring, e.g., a compression spring, extension spring, leafspring, flex arm spring, etc. Spring 2512 may have a first end 2520coupled to applicator housing 2502 and a second end coupled to needlecarrier assembly 2508. Spring 2520 may be configured to, upon activationof drive assembly 2510, drive needle carrier assembly 2508 in the distaldirection. In some embodiments, spring 2512 may be pre-loaded, e.g., atthe factory. In some other embodiments, spring 2512 may be loaded by anaction of the user of applicator 2500.

Drive assembly 2510 further includes a spring 2528 that may be coupledto an applicator base 2530 of applicator 2500. In some embodiments,spring 2528 may be a compression spring, extension spring, leaf spring,flex arm spring, etc. In some embodiments, spring 2528 may bepre-loaded, e.g., at the factory. In some other embodiments, spring 2528may be loaded by an action of the user. In yet other embodiments, spring2528 may be loaded by unloading of spring 2512. Spring 2528 may compriseone or more portions configured to drive needle carrier assembly 2508 inthe proximal direction from the distal insertion position, as will bedescribed in more detail below.

FIG. 26A-26D illustrate several cutaway views and a bottom view ofseveral features of applicator 2500 of FIG. 25, according to someembodiments. FIG. 26A illustrates a perspective cutaway view ofapplicator 2500 including applicator housing 2502, activation element2504, applicator base 2530 including protrusion 2602, spring 2512, leafspring(s) 2528, needle carrier assembly 2508, holder 2524, and on-skinsensor assembly 160. Each of these components may have functionality aspreviously described in connection with at least FIG. 25.

FIG. 26B illustrates a perspective view of several features of holder2524, applicator base 2530 and activation element 2504. Spring 2512 isconfigured to be coupled to applicator housing 2502 at a first end andto holder 2524 at a second end. In a pre-activation state, spring 2512may be configured to store energy for driving holder 2512 (and needlecarrier assembly 2508) in the distal direction to the distal insertionposition upon activation. Holder 2524 comprises an axle 2614 configuredto snap into applicator base 2530 such that holder 2524 is configured topivot in a substantially circular arc about axle 2614. In FIG. 26B,activation element 2504 is illustrated as comprising a protrusion 2612configured to guide holder 2524 in the pre-activation position shownuntil activation element 2504 is activated, thereby displacingprotrusion 2612 from its pre-activation orientation relative to holder2524 and releasing holder 2524. FIG. 26B further illustrates that leafspring(s) 2528 are not coupled to holder 2524. Instead, leaf spring(s)2528 are coupled to needle carrier assembly 2508 and are configured todrive needle carrier assembly 2508 in the proximal direction from thedistal insertion position. Although activation element 2504 is shown asa button, the present disclosure further contemplates activation element2504 as a switch, a toggle, a slide, a trigger, a knob, a rotatingmember, a component that deforms and/or flexes or any other suitablemechanism for activating a drive assembly of applicator 2500. Moreover,although activation element 2504 is illustrated as being disposed on aside of applicator housing 2502, the present disclosure contemplates anyother location, e.g., on a top, bottom, or other side location ofapplicator housing 2502, and/or any other angle of disposition withrespect to applicator housing 2502.

FIG. 26C illustrates an exploded perspective view of needle carrierassembly 2508, insertion element 2674, and holder 2524. Insertionelement 2674 is coupled to needle carrier assembly 2508. In someembodiments, insertion element 2674 comprises an open-sided needleconfigured to guide and insert sensor 138 of on-skin sensor assembly 160(e.g., FIG. 1) into skin 130 of the host. Insertion assembly 2508 iscoupled at a first end to axle 2614 of holder 2524. Insertion assembly2508 further comprises a retention element 2622 configured to releasablycouple a second end of needle carrier assembly 2508 to holder 2524.Insertion assembly 2508 further comprises a retention element 2604configured to releasably couple on-skin sensor assembly 160 to needlecarrier assembly 2508 and holder 2524. In some embodiments, retentionelement 2604 may comprise a snap fit, friction fit, interferencefeature, elastomeric grip and/or adhesive configured to couple on-skinsensor assembly 160 with needle carrier assembly 2508 and/or holder2524. Spring 2512 is configured to, upon activation of applicator 2500,drive needle carrier assembly 2508 and holder 2524 in the distaldirection along a circular arc defined by axle 2614 to the distalinsertion position. Spring 2512 transfers at least a portion of itsstored energy to leaf spring(s) 2528 as needle carrier assembly 2508 isdriven in the distal direction along the circular arc. In some otherembodiments, leaf spring(s) 2528 may be pre-loaded such that spring 2512does not transfer stored energy to leaf spring(s) 2528. As needlecarrier assembly 2508 is driven in the distal direction, a protrusion2602 of applicator base 2530 is configured to deflect retention element2622 sufficiently to separate needle carrier assembly 2508 from holder2524 substantially at the distal insertion position, thereby uncouplingthe second end of needle carrier assembly 2508 from holder 2524.Accordingly, from the distal insertion position, leaf spring(s) 2528,now loaded, are configured to drive needle carrier assembly 2508 in theproximal direction from the distal insertion position, along thecircular arc, to the proximal retraction position.

FIG. 26D illustrates a portion 2632 of activation element 2504 coupledto applicator housing 2502 and configured to act as a return spring,returning activation element 2504 to its pre-activation position afteractivation. For example, as activation element 2504 is pressed to theright as shown in FIG. 26D, portion 2632 is deformed against applicatorhousing 2502, thereby functioning substantially as a spring, which whenunloaded, returns activation element 2504 to its pre-activationposition.

FIGS. 27A-27E illustrate several cross-sectional views of applicator2500 of FIG. 25 during operation, according to some embodiments. FIG. 86illustrates relationships between axle 2614, insertion element 2674, anda circular arc 8602 travelled by insertion element 2674 during insertionand retraction, according to some embodiments. FIG. 27A illustratesapplicator 2500 at the time of activation. For example, activationelement 2504 is illustrated in an activated position, e.g., pushedinwardly, which releases holder 2524 from its immobilized,pre-activation state. Spring 2512, needle carrier assembly 2508,insertion element 2674, holder 2524, and on-skin sensor assembly 160 areall shown in their pre-activation positions.

FIG. 27B illustrates applicator 2500 during activation. Spring 2512 isdriving holder 2524, and so releasably coupled needle carrier assembly2508, insertion element 2674, and on-skin sensor assembly 160, in thedistal direction along the circular arc 8602 (see FIG. 86) defined byaxle 2614. In some embodiments, a radius 8604 (see FIG. 86) of thecircular arc 8602 may be between 20 millimeters (mm) and 80 mm,inclusive, although radiuses larger or smaller than this range are alsocontemplated.

With respect to FIG. 86, the radius 8604 of this circular arc 8602 maydepend on one or more of a distance 8606 from the skin 130 of the hostto axle 2614, a height 8608 of the on-skin sensor assembly 160 from abottom opening or surface of applicator 2500 or from axle 2614, and/or alocation of sensor 138 within on-skin sensor assembly 160. Selection ofa radius 8604 may be made at least in part to minimize tissue trauma,optimize deployment of sensor 138, and to minimize insertion and/orretraction friction between the insertion member and the tissue of thehost.

For example, with respect to FIGS. 27A and 86, an angle 2710 between aneedle axis and a bottom plane of on-skin sensor assembly may becalculated such that a minimum offset is achieved between the straightneedle path and the ideal curved profile 8602. In some embodiments, ithas been determined that an approximately 71 degree angle between theneedle axis and the bottom plane of on-skin sensor assembly producesless lateral motion of the tip of the insertion element 2674 within theskin of the host compared to an approximately 90 degree angle betweenthe needle axis and the bottom plane of on-skin sensor assembly.However, this angle may depend on at least some of the same factorsaffecting an ideal radius of the circular arc.

Moreover, various needle geometries may be utilized, including, but notlimited to, straight needle geometries, kinked needle geometries (e.g.,two or more substantially straight portions with one or more bendsdisposed therebetween), and fully or partially curved needle geometries(e.g., a curved distal portion configured to at least partially piercethe skin of the host with or without a straight proximal portion), asdescribed in more detail in connection with at least FIGS. 47-50 and80A-B.

FIG. 27C illustrates applicator 2500 in the distal insertion position.Spring 2512 has driven holder 2524, and so releasably coupled needlecarrier assembly 2508, insertion element 2674, and on-skin sensorassembly 160, in the distal direction to the distal insertion position.In addition, protrusion 2602 of applicator base 2530 has deflectedretention arm 2622 sufficiently to release the second end of needlecarrier assembly 2508 from holder 2524 in preparation for movement inthe proximal direction from the distal insertion position.

FIG. 27D illustrates applicator 2500 during retraction. Spring 2512remains unloaded, pinning holder 2524 in the distal insertion position.However, leaf spring(s) 2528, still in contact with now-released needlecarrier assembly 2508, drive needle carrier assembly 2508 and coupledinsertion element 2674 in the proximal direction from the distalinsertion position to the proximal retraction position. Retentionelement(s) 2604 are released from on-skin sensor assembly 160 by virtueof spring 2512 pinning holder 2524, and so on-skin sensor assembly 160disposed thereunder, in the distal insertion position. In someembodiments, retention element(s) 2604 may comprise snap fits, frictionfits, interference features, elastomeric grips and/or adhesives.

FIG. 27E illustrates applicator 2500 in the proximal retractionposition. Leaf spring(s) 2528 have driven needle carrier assembly 2508and insertion element 2674 in the proximal direction to the proximalretraction position. Applicator 2500 may then be released from the skinof the host, whereby all portions of the applicator 2500 will be removedfrom the skin of the host except the on-skin sensor assembly 160 and thesensor 138 (e.g., FIG. 1) which is now at least partially inserted intothe skin of the host.

FIGS. 28A-28H illustrate steps to assemble applicator 2500 of FIG. 25,according to some embodiments. FIG. 28A illustrates coupling insertionelement 2674 to needle carrier assembly 2508. In some embodiments,insertion element 2674 may be coupled to needle carrier assembly 2508 atan angle that substantially coincides with the circular path insertionelement 2674 and needle carrier assembly 2508 traverse duringactivation. FIG. 28B illustrates coupling holder 2524 to needle carrierassembly 2508 by coupling needle carrier assembly 2508 to axle 2614 ofholder 2524 and retention element 2622 to holder 2524. FIG. 28Cillustrates coupling on-skin sensor assembly 160 to holder 2524 andneedle carrier assembly 2508 by engaging retention element(s) 2604 ofneedle carrier assembly 25089 with on-skin sensor assembly 160.

FIG. 28D illustrates inserting activation element 2504 into applicatorhousing 2502. FIG. 28E illustrates coupling a first end of spring 2512with applicator housing 2502 through an opening in the bottom ofapplicator housing 2502. FIG. 28F illustrates inserting the assembly2800 c resulting from the step(s) illustrated by FIG. 28C intoapplicator housing 2502. In assembly 2800 c, shown in FIG. 28F, spring2512 is placed in contact with holder 2524 and holder 2524 is secured byprotrusion 2612 of activation element 2504.

FIG. 28G illustrates coupling applicator base 2530 to applicator housing2502. Axle 2614 of holder 2524 is coupled to applicator base 2530 andleaf spring(s) 2528 are placed in contact with needle carrier assembly2508. FIG. 28H illustrates applicator 2500 in assembled form. At thisstep, applicator base 2530 may be coupled to applicator housing 2502,for example, via sonic welding, press-fit, snap-fit, adhesive, or anyother suitable method of securing plastic materials together.

FIG. 29 illustrates an exploded perspective view of yet anotherapplicator 2900 for applying an on-skin sensor assembly to skin 130 of ahost, according to some embodiments. Applicator 2900 may include anapplicator housing 2902 having an opening at its bottom and configuredto house at least one or more mechanisms utilized to apply on-skinsensor assembly 160 to skin 130 of a host.

Applicator 2900 includes an activation element 2904 configured toactivate a drive assembly of applicator 2900. In some embodiments,activation element 2904 may be a button, a switch, a toggle, a slide, atrigger, a knob, a rotating member, a component that deforms and/orflexes or any other suitable mechanism for activating a drive assemblyof applicator 2900. Applicator 2900 may further comprise a needlecarrier assembly 2908, including an insertion element (see FIG. 30)configured to insert sensor 138 of on-skin sensor assembly 160 (e.g.,FIG. 1) into skin 130 of the host. In some embodiments, the insertionelement comprises a needle, for example, an open sided-needle, a needlewith a deflected-tip, a curved needle, a polymer-coated needle, ahypodermic needle, or any other suitable type of needle or structure, aswill be described in more detail in connection with at least FIGS. 47-50and 80A-B. In yet other embodiments, insertion element may comprisesensor 138 itself, sufficiently rigid to be inserted partially into skin130 of the host with minimal or no structural support.

Applicator 2900 may further comprise a drive assembly 2910 configured todrive the insertion element of needle carrier assembly 2908 in a distaldirection to a distal insertion position and in a proximal directionfrom the distal insertion position to a proximal retraction position. Adistal direction may be defined as extending towards an open-ended sideof applicator 2900 along a path needle carrier assembly 2908 isconfigured to travel. The distal direction may also be defined astowards the skin of a user. A proximal direction may be defined as adirection extending in a substantially opposite direction from thedistal direction. In some embodiments, the distal direction and theproximal direction extend along an insertion axis of the insertionelement and of needle carrier assembly 2908.

Drive assembly 2910 may include a rotating drive element 2914 disposedwithin needle carrier assembly 2908 and configured to rotate withrespect to needle carrier assembly 2908 about an axis of rotation 2918parallel with a centerline of needle carrier assembly 2908. In someembodiments, rotating drive element 2914 is configured to rotate in aplane substantially perpendicular to the proximal direction and thedistal direction. In some embodiments, rotating drive element 2914 maycomprise a barrel cam. Rotating drive element 2914 comprises a ridge2916 that defines a variable cam path around at least a portion of acircumference of the rotating drive element. Ridge 2916 is configured toslide along a channel (see FIG. 30) on an inside surface of needlecarrier assembly 2908 as rotating drive element 2914 rotates, therebydriving needle carrier assembly 2908 in the distal direction to thedistal insertion position and then in the proximal direction to theproximal retraction position as defined by the variable cam path ofridge 2916.

Drive assembly 2910 may further include a spring 2912 disposed withinrotating drive element 2914. Spring 2912 may be a torsion spring, or anysuitable type of spring. Spring 2912 may have a first end 2920 coupledto applicator housing 2902 and a second end 2922 coupled to rotatingdrive element 2914. Spring 2912 may be disposed coaxially with rotatingdrive element 2914 and needle carrier assembly 2908. Spring 2920 may beconfigured to, upon activation of drive assembly 2910, rotate rotatingdrive element 2914 in a single direction with respect to needle carrierassembly 2908.

By virtue of rotating drive element 2914 being configured to rotate withrespect to needle carrier assembly 2908, about axis of rotation 2918,and ridge 2916 being restrained to travel in the channel of needlecarrier assembly 2908, rotational motion of rotating drive element 2914,caused by spring 2912, is converted into linear, reciprocating motion ofneedle carrier assembly 2908 and, therefore, insertion element (see FIG.30). More specifically, rotation of rotating drive element 2914 drivesinsertion element 2908 in the distal direction to the distal insertionposition and in the proximal direction from the distal insertionposition to the proximal retraction position.

Applicator 2900 may further include a holder 2924 releasably coupled toneedle carrier assembly 2908 via retention element(s) 2980 andconfigured to guide on-skin sensor assembly 160 while coupled to needlecarrier assembly 2908. In some embodiments, retention element(s) 2980may comprise snap fits, friction fits, interference features,elastomeric grips and/or adhesives configured to couple on-skin sensorassembly 160 with needle carrier assembly 2908 and/or holder 2924.On-skin sensor assembly 160 may be stripped from holder 2924 and/orneedle carrier assembly 2908 once on-skin sensor assembly 160 isdisposed on skin 130 of the host.

FIG. 30 illustrates a perspective cutaway view of a portion ofapplicator 2900 of FIG. 29, according to some embodiments. FIG. 30illustrates at least one protrusion 3024 of needle carrier assembly 2908configured to slide within tracks (not shown in FIG. 30) on an insidesurface of applicator housing 2902 (similar to tracks 622 a-622 c inFIG. 6) that define a linear path of travel for needle carrier assembly2908. FIG. 30 further illustrates channel 3002 in which ridge 2916 ofrotating drive element 2914 is configured to slide as spring 2912rotates rotating drive element 2914 with respect to needle carrierassembly 2908. FIG. 30 further illustrates insertion element 3074coupled to needle carrier assembly 2908.

In some embodiments, holder 2924 further includes a retention element3042 configured to engage with a retention element (not shown in FIG.30) of applicator housing 2902, similar to stop element 644 ofapplicator housing 462 of FIG. 6, and immobilize holder 2924 toapplicator housing 2902 upon needle carrier assembly 2908 reaching thedistal insertion position. Although not shown in FIG. 30, holder 2928may further comprise a protrusion and applicator housing 2902 mayfurther comprise a protrusion configured to prevent holder 2924 fromtravelling beyond the distal insertion position in the distal direction,similar to protrusion 652 and protrusion 654 as previously described inconnection with FIG. 6F.

FIG. 31 illustrates a cutaway view of yet another applicator 3100 for anon-skin sensor assembly of an analyte sensor system, according to someembodiments. In some embodiments, applicator 3100 may include anapplicator housing 3102 configured to house one or more mechanisms forapplying on-skin sensor assembly 160 to skin 130 of a host. Applicator3100 may further comprise a base 3130 coupled to applicator housing 3102and configured to form a bottom of applicator 3100.

Applicator 3100 further includes an activation element (not shown inFIG. 31) configured to activate a drive assembly 3110 of applicator3100. In some embodiments, the activation element may be a button, aswitch, a toggle, a slide, a trigger, a knob, a rotating member, acomponent that deforms and/or flexes or any other suitable mechanism foractivating a drive assembly of applicator 3100. In addition, theactivation element of applicator 3100 may be disposed in any locationand orientation with respect to applicator housing 3102, e.g., a top,any portion of a side, or bottom of applicator housing 3102 and/or atany angle with respect to the portion of applicator housing 2102 inwhich the activation element is disposed. Applicator 3100 may furthercomprise a needle carrier assembly 3108, including an insertion element3174 releasably coupled to on-skin sensor assembly 160 and configured toinsert sensor 138 of on-skin sensor assembly 160 (e.g., FIG. 1) intoskin 130 of the host. In some embodiments, the insertion elementcomprises a needle, for example, an open sided-needle, a needle with adeflected-tip, a curved needle, a polymer-coated needle, a hypodermicneedle, deflected-tip or any other suitable type of needle or structure,as will be described in more detail in connection with at least FIGS.47-50 and 80A-B. In yet other embodiments, insertion element maycomprise sensor 138 itself, sufficiently rigid to be inserted partiallyinto skin 130 of the host with minimal or no structural support,

Drive assembly 3110 may be configured to drive insertion element 3174 ofneedle carrier assembly 3108 in a distal direction to a distal insertionposition and in a proximal direction from the distal insertion positionto a proximal retraction position. Drive assembly 3110 may include aguide member 3138, a spring 3112, a hub 3132 and a reverse togglingelement 3136. guide member 3138 may be coupled to at least one ofapplicator housing 3102 and base 3130 at a first end and/or a secondend, respectively. Spring 3112 may be disposed around guide member 3138such that guide member 3138 extends substantially along a centerline ofspring 3112. Spring 3112 may be any suitable type of spring, e.g., acompression spring, and may have a first end coupled to base 3130 and asecond end coupled to a hub 3132, which is disposed on and configured totravel along guide member 3138. Spring 3120 may be configured to, uponactivation of drive assembly 3110, drive hub 3132 in the proximaldirection along guide member 3138, as shown by the arrow. Reversetoggling element 3136 may function substantially as a lever with afulcrum at or near its midpoint, rotatably coupled to base 3130 orapplicator housing 3102. A first end of reverse toggling element 3136may be in contact with a protrusion 3134 of hub 3132 for at least afirst portion of travel of hub 3132 in the proximal direction and asecond end of reverse toggling element 3136 may be in contact withneedle carrier assembly 3108. Insertion assembly 3108 may be slideablycoupled to guide member 3138 on the side of hub 3132 opposite spring3112.

In operation, upon activation of drive assembly 3110, spring 3112 driveshub 3132 along guide member 3138 in the proximal direction. For a firstportion of travel along guide member 3138, protrusion 3134 of hub 3132is in contact with the first end of reverse toggling element 3136,causing the second end of reverse toggling element 3136 to drive needlecarrier assembly 3138, and so insertion element 3174 and on-skin sensorassembly 160, in the distal direction. After the first portion of travelalong guide member 3138, protrusion 3134 of hub 3132 will clear thefirst end of reverse toggling element 3136 and make contact with theportion of needle carrier assembly 3138 slideably coupled with guidemember 3138. At this point, needle carrier assembly 3108, insertionelement 3174 and on-skin sensor assembly 160 are in the distal insertionposition. For a second portion of travel along guide member 3138 in theproximal direction, hub 3132, still driven by spring 3112, drives needlecarrier assembly 3108, and so insertion element 3174, in the proximaldirection from the distal insertion position to the proximal retractionposition. In this way, drive assembly 3110 converts linear motion ofspring 3112 in a single direction, e.g., the proximal direction, intoreciprocating linear motion in the distal direction and then theproximal direction.

FIG. 32A illustrates an exploded perspective view of yet anotherapplicator 3200 for an on-skin sensor assembly of an analyte sensorsystem, according to some embodiments. Applicator 3200 may include anapplicator housing 3202 configured to house at least one or moremechanisms utilized to apply the on-skin sensor assembly 160 to skin 130of a host. Applicator 3200 may further include a base 3230 coupled to abottom opening of applicator housing 3202. Base 3230 defines a bottomsurface of applicator 3200 and a plane for application of on-skin sensorassembly 160 to skin 130 of a host.

Applicator 3200 includes an activation element 3204 configured toactivate a drive assembly of applicator 3200. In some embodiments,activation element 3204 may be a button, a switch, a toggle, a slide, atrigger, a knob, a rotating member, a component that deforms and/orflexes or any other suitable mechanism for activating a drive assemblyof applicator 460.

Applicator 3200 may further comprise a needle carrier assembly 3208,including an insertion element 3274 configured to insert sensor 138 ofon-skin sensor assembly 160 into skin 130 of the host (e.g., FIG. 1). Insome embodiments, the insertion element comprises a needle, for example,an open sided-needle, a needle with a deflected-tip, a curved needle, apolymer-coated needle, a hypodermic needle, or any other suitable typeof needle or structure, as will be described in more detail inconnection with at least FIGS. 47-50 and 80A-B. In yet otherembodiments, insertion element may comprise sensor 138, sufficientlyrigid to be inserted partially into skin 130 of the host with minimal orno structural support.

Applicator 3200 may further include a holder 3224 releasably coupled toneedle carrier assembly 3208 and configured to guide on-skin sensorassembly 160 while coupled to needle carrier assembly 3208. As will bedescribed in more detail below, on-skin sensor assembly 160 may bestripped from holder 3224 and needle carrier assembly 3208 once on-skinsensor assembly 160 is disposed on skin 130 of the host.

Applicator 3200 may further comprise a drive assembly configured todrive insertion element 3274 and needle carrier assembly 3208 in thedistal direction to the distal insertion position and in the proximaldirection from the distal insertion position to the proximal retractionposition. Drive assembly 3210 may include a first spring 3212 and asecond spring 3228. First spring 3212 may be a compression spring, orany suitable type of spring, and may have a first end coupled toapplicator housing 3202 and a second end coupled to holder 3224. Firstspring 3212 is configured to, upon activation of drive assembly 3210,drive holder 3224, and also coupled needle carrier assembly 3208,insertion element 3274 and on-skin sensor assembly 160, in the distaldirection to the distal insertion position. Substantially at the distalinsertion position, needle carrier assembly 3208 may decouple fromholder 3224 and on-skin sensor assembly 160.

Second spring 3228 may be a compression spring, or any suitable type ofspring, and may have a first end coupled to holder 3224 and a second endcoupled to needle carrier assembly 3208. Second spring 3228 isconfigured to drive needle carrier assembly 3208, and also insertionelement 3274, in the proximal direction from the distal insertionposition to the proximal retraction position. In some embodiments, firstspring and/or second spring can be preloaded, partially loaded, orunloaded.

FIG. 32B illustrates an exploded perspective view 3250 of needle carrierassembly 3208 coupled to insertion element 3274, second spring 3228,holder 3224 and on-skin sensor assembly 160.

FIG. 33A-33E illustrate perspective cutaway views of several features ofapplicator 3200 of FIGS. 32A-32B, according to some embodiments. FIG.33A illustrates a perspective cutaway view of the entire applicator3200, including applicator housing 3202, activation element 3204, firstspring 3212, needle carrier assembly 3208 coupled to insertion element3274, holder 3224 coupled to on-skin sensor assembly 160, and base 3230.Each of these components may have functionality as previously describedin connection with at least FIGS. 32A-32B.

FIG. 33B illustrates a magnified perspective cutaway view of a retentionelement 3312 of holder 3224 releasably coupled to application housing3202. Retention element 3312 is configured to prevent holder 3224 fromtraveling in the distal direction and, therefore, spring 3212 fromunloading. Activation mechanism 3204, when activated, is configured todeflect retention element 3312 sufficiently to decouple it fromapplicator housing 3202, thereby freeing holder 3224 to travel in thedistal direction, driven by spring 3212.

FIG. 33C illustrates a magnified perspective cutaway view of a retentionelement 3342 of needle carrier assembly 3208 configured to releasablycouple needle carrier assembly 3208 to holder 3224. As shown, retentionelement 3342 may have a sloped surface configured to come in contactwith a protrusion (not shown in FIG. 33) of the applicator housing 3202or base 3230 (not shown in FIG. 33) that is configured to deflectretention element 3342 sufficiently to decouple needle carrier assembly3208 from holder 3224 when needle carrier assembly 3208 is at or nearthe distal insertion position.

FIG. 33D illustrates a perspective view of a plurality of retentionelements 3372 a, 3372 b of needle carrier assembly 3208 configured topass through holder 3224 and releasably couple on-skin sensor assembly160 to holder 3224 and to needle carrier assembly 3208. As previouslydescribed, at the distal insertion position, deflected retention element3342 decouples needle carrier assembly 3208 from holder 3224, allowingsecond spring 3228 to drive needle carrier assembly 3208 in the proximaldirection. As needle carrier assembly 3208 is driven in the proximaldirection, retention elements 3372 a, 3372 b detach from on-skin sensorassembly 160. Although two retention elements are illustrated, anynumber of retention elements are contemplated. In some embodiments,retention element(s) 3372 a, 3372 b may comprise snap fits, frictionfits, interference features, elastomeric grips and/or adhesivesconfigured to couple on-skin sensor assembly 160 with needle carrierassembly 3208 and/or holder 3224. Moreover, alternative mechanisms thatmay perform such retention and release actions are further described inconnection with at least FIGS. 35A-37C below.

FIG. 33E illustrates a perspective cutaway view of a retention element3346 of holder 3224 and a retention element 3348 of applicator housing3202 configured to immobilize needle carrier assembly 3208 to holder3346 upon needle carrier assembly 3208 reaching the distal insertionposition. This interaction immobilizes insertion element 3274 in theproximal retraction position, thereby ensuring the end of insertionelement 3274 is not exposed out the bottom of applicator 3200.

A brief description of the operation of applicator 3200 follows withrespect to FIGS. 34A-34F, which illustrate several perspective views ofthe applicator of FIG. 32 during operation, according to someembodiments.

FIG. 34A illustrates a state of applicator 3200 at activation.Activation element 3204 is illustrated in the process of beingactivated, having been pushed down by a user, for example. Activationelement 3204 deflects retention element 3312 such that holder 3224 isnot prevented from traveling in the distal direction. Holder 3224,needle carrier assembly 3208, insertion element 3274, first spring 3212and second spring 3228 are all shown in pre-activation positions.

FIG. 34B illustrates applicator 3200 during activation. Activationelement 3204 is illustrated in the activated position. Spring 3212 isdriving holder 3224, and also needle carrier assembly 3208, insertionelement 3274, and on-skin sensor assembly 160, in the distal directiontoward the distal insertion position.

FIG. 34C illustrates applicator 3200 during activation, as needlecarrier assembly 3208 approaches the distal insertion position.Activation element 3204 is illustrated in the activated position.Insertion assembly 3208, insertion element 3274, holder 3224 and on-skinsensor assembly 160 are driven in the distal direction to the distalinsertion position. At or near this distal insertion position, at leasta portion of insertion element 3274 as well as at least a portion ofsensor 138 of on-skin sensor assembly 160 may be inserted into the skinof the host. At this position, retention element 3342 is deflected by aportion of applicator housing 3302 or base 3230, thereby decouplingneedle carrier assembly 3208 from holder 3224.

FIG. 34D illustrates applicator 3200 during activation. Activationelement 3204 is illustrated in the activated position. Second spring3228 drives needle carrier assembly 3208 and insertion element 3274 inthe proximal direction from the distal insertion position. Although notshown in FIG. 34D, once needle carrier assembly reaches the proximalretraction position, retention elements 3346 and 3348 may be engagedwith one another immobilizing needle carrier assembly 3208 and insertionelement 3274 in the proximal retraction position, thereby maintaininginsertion element 3274 in a locked, retracted position.

FIG. 35A-35C illustrate several cross-sectional views of an on-skinsensor assembly retention mechanism of applicator 3200 of FIG. 32,according to some embodiments. The retention mechanism described inconnection with FIGS. 35A-35C is similar to the retention mechanismpreviously described in connection with FIGS. 6A-6H. FIG. 35Aillustrates the retention mechanism while applicator 3200 is in thepre-activated state. Retention element 3372 a is illustrated as aportion of holder 3224 and configured to releasably couple on-skinsensor assembly 160 to holder 3224 as needle carrier assembly 3208travels in the distal direction to the distal insertion position, and todecouple on-skin sensor assembly 160 from holder 3224 as needle carrierassembly 3208 travels in the proximal direction from the distalinsertion position towards the proximal retraction position.Specifically, retention element 3372 a may comprise a first end 3376 aand a second end 3378 a. The second end may be releasably coupled toon-skin sensor assembly 160 in the pre-activation state. As previouslystated, retention element(s) 3372 a, 3372 b may comprise snap fits,friction fits, interference features, elastomeric grips and/or adhesivesconfigured to couple on-skin sensor assembly 160 with needle carrierassembly 3208 and/or holder 3224. FIG. 35A further illustratesapplicator housing 3202 comprising an optional reinforcing element 3510configured to prevent lateral motion of retention element 3372 a in theproximal starting position, thereby supporting releasable coupling ofsecond end 3378 a of retention element 3372 a with on-skin sensorassembly 160.

FIG. 35B illustrates applicator 3200 in the distal insertion positionafter activation. As needle carrier assembly 3208 travels in the distaldirection to the distal insertion position, retention element 3342 ofneedle carrier assembly 3208 is released from holder 3224. The secondend of retention element 3372 a may still be releasably coupled toon-skin sensor assembly 160. FIG. 35B further illustrates optionalreinforcing element 3510 as no longer being in physical contact withretention element 3372 a in the distal insertion position, therebyallowing for the uncoupling of second end 3378 a of retention element3372 a from on-skin sensor assembly 160.

FIG. 35C illustrates applicator 3200 where needle carrier assembly 3208is moving in the proximal direction from the distal insertion position.Since retention element 3342 of needle carrier assembly 3208 wasuncoupled from holder 3224 at the distal insertion position, as needlecarrier assembly 3208 travels back in the proximal direction, needlecarrier assembly 3208 separates from holder 3224. As needle carrierassembly 3208 travels in the proximal direction, first end 3376 a ofretention element 3372 a is deflected by needle carrier assembly 3208,thereby decoupling second end 3378 a of retention element 3372 a fromon-skin sensor assembly 160. FIG. 35C further illustrates optionalreinforcing element 3510 as no longer being in physical contact withretention element 3372 a in the distal insertion position.

FIG. 36A-36C illustrate several cross-sectional views of another on-skinsensor assembly retention mechanism of applicator 3200 of FIG. 32,according to some embodiments. FIG. 36A illustrates the retentionmechanism while applicator 3200 is in the pre-activated state. Retentionelement 3372 a is illustrated as a portion of needle carrier assembly3208 and is configured to releasably couple on-skin sensor assembly 160to holder 3224 as needle carrier assembly 3208 travels in the distaldirection to the distal insertion position, and to decouple on-skinsensor assembly 160 from holder 3224 as needle carrier assembly 3208travels in the proximal direction from the distal insertion positiontowards the proximal retraction position. Specifically, retentionelement 3372 a may releasably couple on-skin sensor assembly 160 asneedle carrier assembly 3208 travels in the distal direction to thedistal insertion position. FIG. 36A further illustrates applicatorhousing 3202 comprising an optional reinforcing element 3610 configuredto prevent lateral motion of retention element 3372 a and/or retentionelement 3342 in the proximal starting position, thereby supportingreleasable coupling of retention element 3372 a with on-skin sensorassembly 160.

FIG. 36B illustrates applicator 3200 at the distal insertion position.Retention element 3342 of needle carrier assembly 3208 is uncoupled fromholder 3224 at the distal insertion position, retention element 3224being deflected by a portion of applicator housing 3202 or an applicatorbase of applicator housing 3202 sufficient for retention element 3224 toclear a stop element of needle carrier assembly. Accordingly, needlecarrier assembly 3208 separates from holder 3224 as needle carrierassembly 3208 travels back in the proximal direction by a force providedby spring 3228. Rather than being physically deflected in orientation asneedle carrier assembly 3208 travels in the proximal direction,retention element 3372 a is formed to be easily deflected or deformedsimply by the separation of holder 3224 from needle carrier assembly3208. FIG. 36B further illustrates optional reinforcing element 3610 asno longer being in physical contact with retention element 3372 a and/orretention element 3342 in the distal insertion position, therebyallowing for the uncoupling of retention element 3372 a from on-skinsensor assembly 160 and/or the uncoupling of holder 3224 from needlecarrier assembly 3208.

FIG. 36C illustrates needle carrier assembly 3208 moving in the proximaldirection from the distal insertion position of FIG. 36B. As shown,retention element 3372 a has been released from on-skin sensor assembly160 by separation of needle carrier assembly 3208 from holder 3224, andneedle carrier assembly 3208 is driven in the proximal direction by aforce provided by spring 3228. FIG. 36C further illustrates optionalreinforcing element 3610 as no longer being in physical contact withretention element 3372 a and/or retention element 3342 in the proximalretracted position.

FIG. 37A-37C illustrate several cross-sectional views of yet anotheron-skin sensor assembly retention mechanism of applicator 3200 of FIG.32, according to some embodiments. FIG. 37A illustrates applicator 3200in the pre-activated position. Retention element 3372 a is illustratedin FIG. 37A as an integral portion of holder 3208 and is configured toreleasably couple on-skin sensor assembly 160 to holder 3224 as needlecarrier assembly 3208 travels in the distal direction to the distalinsertion position, and to decouple on-skin sensor assembly 160 fromholder 3224 as needle carrier assembly 3208 travels in the proximaldirection from the distal insertion position towards the proximalretraction position. Specifically, retention element 3372 a mayreleasably couple on-skin sensor assembly 160 as needle carrier assembly3208 travels in the distal direction to the distal insertion position.FIG. 37A further illustrates applicator housing 3202 comprising anoptional first reinforcing element 3710 configured to prevent lateralmotion of retention element 3342 in the proximal retracted position.FIG. 37A further illustrates needle carrier 3208 comprising an optionalsecond reinforcing element 3712 configured to prevent lateral motion ofretention element 3372 a, thereby supporting releasable coupling ofretention element 3372 a with on-skin sensor assembly 160.

FIG. 37B illustrates needle carrier assembly 3208 in the distalinsertion position. Retention element 3342 of needle carrier assembly3208 is uncoupled from holder 3224 at the distal insertion position.Accordingly, needle carrier assembly 3208 separates from holder 3224 asneedle carrier assembly 3208 travels back in the proximal directionunder influence of a force provided by spring 3228 as spring 3228unloads, pushing against holder 3224 and needle carrier assembly 3208.FIG. 37B further illustrates optional first reinforcing element 3710 asno longer being in physical contact with retention element 3342 in thedistal insertion position, thereby allowing for the uncoupling of holder3224 from needle carrier assembly 3208. Optional second reinforcingelement 3712 is still illustrated as being in physical contact withretention element 3372 a in the distal insertion position.

FIG. 37C illustrates needle carrier assembly as it begins to travel inthe proximal direction, after retention element 3372 a of needle carrierassembly 3208 is uncoupled from holder 3224. Rather than beingphysically deflected in orientation as needle carrier assembly 3208travels in the proximal direction, as in FIGS. 35A-35C, retentionelement 3372 a detaches from on-skin sensor assembly 160 simply by theuser removing applicator 3200 from the skin. In some embodiments, anadhesive patch that holds on-skin sensor assembly 160 to the skin of thehost provides sufficient bonding strength to decouple on-skin sensorassembly 160 from the skin of the host when applicator 3200 is removedfrom the skin. FIG. 37C further illustrates optional first reinforcingelement 3710 as no longer being in physical contact with retentionelement 3372 a in the proximal retracted position, thereby supportinguncoupling of retention element 3372 a from on-skin sensor assembly 160.

FIG. 38 illustrates a perspective view of an applicator 3800 similar tothose shown in FIG. 32, including an activation element 3804 on a sideof an applicator housing 3802, according to some embodiments. Applicator3800 may have substantially the same features as either applicator 3200of FIG. 32, except that activation element 3804 is located on a side ofapplicator housing 3802, rather than on a top of the applicator housing.Such an arrangement may provide for an applicator having a reducedheight compared to top-activated applicators, though potentially havingan increased width or diameter compared to the top-activatedapplicators.

FIG. 39 illustrates a cutaway view of a portion of applicator 3800 ofFIG. 38, according to some embodiments. Activation element 3804 may beconfigured to, upon activation, deflect a retention element 3902 ofholder 3824 configured to prevent holder 3824 from traveling in thedistal direction. All other features of applicator 3800 not discussedmay be substantially as previously described for either applicator 3200of FIG. 32.

FIGS. 40A-40G illustrate several perspective views of an assemblyprocess for the applicator of FIG. 32, according to some embodiments.FIG. 40A illustrates inserting second spring 3228 into holder 3224. FIG.40B illustrates next inserting insertion element 3274 into needlecarrier assembly 3208 and then inserting insertion element 3274 intoneedle carrier assembly 3208 into holder 3224. In some embodiments,inserting insertion element 3274 into needle carrier assembly 3208 intoholder 3224 pre-compresses second spring 3228. FIG. 40C illustratescoupling on-skin sensor assembly 160 to at least one of holder 3224 andneedle carrier assembly 3208 by coupling retention elements (not shownin FIG. 40C) of holder 3224 or of needle carrier assembly 3208 toattachment points (not shown in FIG. 40C) of on-skin sensor assembly160.

FIG. 40D illustrates coupling activation element 3204 to applicatorhousing 3202. In FIG. 40D, activation element 3204 is coupled on a topof applicator housing 3202. In some embodiments, activation element 3204may be pressed into an opening of applicator housing 3202 configured toreceive activation element 3204. However, in other embodiments,applicator housing 3202 may accommodate activation element 3204 in otherlocations, for example, an upper, medial or lower side of applicatorhousing. FIG. 40E illustrates inserting first spring 3212 intoapplicator housing 3202. FIG. 40F illustrates inserting the assemblydescribed in FIG. 40C (comprising holder 3224, second spring 3228,needle carrier assembly 3208, insertion element 3274 and on-skin sensorassembly 160) into applicator housing 3202. In some embodiments, the actof inserting the assembly described in FIG. 40C pre-compresses firstspring 3212. FIG. 40G illustrates coupling base 3230 to applicatorhousing 3202.

On-Skin Sensor Assembly Retention Mechanisms

In some embodiments of applicators described herein, on-skin sensorassembly 160 is held in place during at least travel in the distaldirection to the distal insertion position. In some such embodiments,on-skin sensor assembly 160 is then released or decoupled from a portionof the applicator during application to the skin of the host so that aneedle carrier assembly and insertion element may travel back in theproximal direction. FIGS. 41A-45 illustrate several alternativeretention mechanisms that may be utilized in any of the applicatorsdescribed herein.

FIGS. 41A-41B illustrate an exemplary on-skin sensor assembly retentionmechanism of an applicator for an analyte sensor system, according tosome embodiments. The retention mechanism illustrated by FIGS. 41A-41Bmay be considered a first on-skin sensor assembly retentionconfiguration, and is similar to the retention mechanism previouslydescribed in connection with FIG. 5.

FIG. 41A illustrates a retention mechanism in a state where on-skinsensor assembly 160 is retained, while FIG. 41B illustrates theretention mechanism in a state where on-skin sensor assembly 160 isdecoupled.

FIG. 41A illustrates retention elements 4172 a, 4172 b of a holder 4124configured to releasably couple on-skin sensor assembly 160 to holder4124 as needle carrier assembly 4108 (and so insertion element 4172,holder 4124, and on-skin sensor assembly 160) travels in the distaldirection to the distal insertion position. Specifically, retentionelements 4172 a, 4172 b may each comprise a first end 4176 a, 4176 b, asecond end 4178 a, 4178 b, and a pivot point 4180 a, 4180 b. First end4176 a, 4176 b is immobilized in a respective guide 4174 a, 4174 b ofneedle carrier assembly 4108 and each of retention elements 4172 a, 4172b is immobilized against interference points 4182 a, 4182 b of needlecarrier assembly 4108, thereby releasably coupling and immobilizingsecond end 4178 a, 4178 b to attachment points 4162 a, 4162 b of on-skinsensor assembly 160 as needle carrier assembly 4108 travels in thedistal direction to the distal insertion position. In some embodiments,the profile of slots 4174 a, 4174 b may be such that the sides of slots4174 a, 4174 b exert a force on first ends 4176 a, 4176 b of retentionelements 4172 a, 4172 b sufficient to hold second ends 4178 a, 4178 b ofretention elements 4172 a, 4172 b in engagement with attachment points4162 a, 4162 b of on-skin sensor assembly 160. Although two retentionelements are illustrated, any number of retention elements arecontemplated.

FIG. 41B illustrates the retention mechanism as needle carrier assembly4108 and insertion element 4174 travel in the proximal direction fromthe distal insertion position to the proximal retraction position. Asneedle carrier assembly 4108 travels back in the proximal direction,needle carrier assembly 4108 separates from holder 4124, therebyremoving first ends 4176 a, 4176 b of retention elements 4172 a, 4172 bfrom respective slots 4174 a, 4174 b, allowing first ends 4176 a, 4176 bto deflect inward and second ends 4178 a, 4178 b of retention elements4172 a, 4172 b to deflect outward from attachment points 4162 a, 4162 bof on-skin sensor assembly 160 as retention elements 4172 a, 4172 brotate about pivot points 4180 a, 4180 b.

FIGS. 42A-42B illustrate an exemplary on-skin sensor assembly retentionmechanism of an applicator for an analyte sensor system, according tosome embodiments. The retention mechanism illustrated by FIGS. 42A-42Bmay be considered a second on-skin sensor assembly retentionconfiguration, and is similar to the retention mechanism previouslydescribed in connection with FIG. 36. FIG. 42A illustrates a retentionmechanism in a state where on-skin sensor assembly 160 is retained,while FIG. 42B illustrates the retention mechanism in a state whereon-skin sensor assembly 160 is decoupled.

FIG. 42A illustrates retention elements 4272 a, 4272 b as portions ofneedle carrier assembly 4208 that pass through or around needle carrierassembly 4208, rather than as portions of holder 4224. Retentionelements 4272 a, 4272 b are configured to releasably couple on-skinsensor assembly 160 to holder 4228 as needle carrier assembly 4208 (andso an insertion element, holder 4224, and on-skin sensor assembly 4224)travels in the distal direction to the distal insertion position.

FIG. 42B illustrates the retention mechanism as needle carrier assembly4208 and insertion element 4274 travel in the proximal direction fromthe distal insertion position to the proximal retraction position. Asneedle carrier assembly 4208 travels in the proximal direction, needlecarrier assembly 2508 separates from holder 4224 and retention elements4272 a, 4272 b are uncoupled from respective attachment points 4262 a,4262 b of on-skin sensor assembly 160. Rather than being physicallydeflected in orientation as needle carrier assembly 4208 travels in theproximal direction, as described for retention elements 4172 a, 4172 bof FIGS. 41A-41B, retention elements 4272 a, 4272 b are pulled out ofattachment points 4262 a, 4262 b by the energy of the retraction.

FIGS. 43A-43B illustrate an exemplary on-skin sensor assembly retentionmechanism of an applicator for an analyte sensor system, according tosome embodiments. The retention mechanism illustrated by FIGS. 43A-43Bmay be considered a passive snap design. FIG. 43A illustrates aretention mechanism in a state where on-skin sensor assembly 160 isretained, while FIG. 43B illustrates the retention mechanism in a statewhere on-skin sensor assembly 160 is decoupled.

FIG. 43A illustrates retention elements 4372 a, 4372 b as portions of aholder 4324. Retention elements 4372 a, 4372 b are configured toreleasably couple on-skin sensor assembly 160 to holder 4324 as needlecarrier assembly 4308 (and so an insertion element, holder 4324, andon-skin sensor assembly 4324) travels in the distal direction to thedistal insertion position. FIG. 43A further illustrates protrusions 4380a, 4380 b of needle carrier assembly 4308 configured to physicallycontact retention elements 4372 a, 4372 b of holder 4324 therebypreventing retention elements 4372 a, 4372 b from disengaging fromon-skin sensor assembly 4324 while needle carrier assembly 4308 is incontact with holder 4324.

FIG. 43B illustrates the retention mechanism as needle carrier assembly4308 travels in the proximal direction from the distal insertionposition to the proximal retraction position. As needle carrier assembly4308 travels in the proximal direction, needle carrier assembly 4308separates from holder 4324. Although not shown in FIGS. 43A-43B, holder4324 may be immobilized to an applicator housing or base by one or moreretention elements, similar to retention elements 642, 644 of FIG. 6E.Accordingly, retention elements 4372 a, 4372 b may be uncoupled fromrespective attachment points 4362 a, 4362 b of on-skin sensor assembly160 as the applicator is removed from the skin of the host. In someembodiments, an adhesive patch that holds on-skin sensor assembly 160 tothe skin of the host provides sufficient bonding strength to decoupleon-skin sensor assembly 160 from the skin of the host when theapplicator is removed from the skin.

FIG. 44 illustrates another portion of an exemplary on-skin sensorassembly retention mechanism of an applicator for an analyte sensorsystem, according to some embodiments. FIG. 44 illustrates a needlecarrier assembly 4408, a holder 4424, and on-skin sensor assembly 160.Contrary to several previous embodiments of retention mechanisms foron-skin sensor assembly 160, needle carrier assembly 4408 comprises atleast one retention element 4472 a and holder 4424 comprises at leastone alignment element 4473 a, in which retention element 4472 a isconfigured to releasably couple to on-skin sensor assembly 160, andalignment element 4473 a is configured to align on-skin sensor assembly160 within the applicator. This distribution of retention elementsbetween both a needle carrier assembly and a holder may be implementedfor any on-skin sensor assembly retention mechanism described herein.

FIGS. 45 and 46 illustrate portions of exemplary on-skin sensor assemblyretention mechanisms of an applicator for an analyte sensor system,according to some embodiments. FIGS. 45 and 46 illustrate a needlecarrier assembly 4508, 4608, a rotating drive element 4514, 4614 similarto that previously described in connection with FIG. 5, and on-skinsensor assembly 160. Accordingly, the retention mechanisms of FIGS. 45and 46 may function similarly to that described in FIG. 5. Rotatingdrive element 4514, 4614 may be a wheel cam and may comprise a cam lobe4518 (e.g., a ramp or protrusion, not shown in FIG. 46, see FIG. 45)disposed along at least a portion of a circumference of rotating driveelement 4514, 4614. In FIG. 45, as rotating drive element 4514 isrotated, protrusion 4518 may travel alongside needle carrier assembly4508 and come into contact with and increasingly apply a force toon-skin sensor assembly 160 such that on-skin sensor assembly 160decouples from needle carrier assembly 4508. In FIG. 46, as rotatingdrive element 4614 is rotated, the protrusion may travel at leastpartially through a guide or slot 4620 in needle carrier assembly 4608and come into contact with and increasingly apply a force to on-skinsensor assembly 160 such that on-skin sensor assembly 160 decouples fromneedle carrier assembly 4608. In this way, rotating drive element 4514,4614 may serve both to drive needle carrier assembly 4508, 4608 in thedistal and proximal directions, as previously described in connectionwith FIG. 5, and to release on-skin sensor assembly 160 upon depositionto the skin of the host.

In some embodiments, on-skin sensor assembly retention mechanisms mayincorporate features to couple an on-skin sensor assembly to the needlecarrier assembly and/or the holder. Methods of coupling on-skin sensorassembly are described in U.S. patent application Ser. No. 15/387,088,which is incorporated herein by reference it its entirety. Fornon-limiting example, on-skin sensor assembly retention mechanisms mayinclude a frangible release (e.g. FIGS. 137-140), a frangible elastomer(e.g. FIGS. 134-136), a releasable adhesive (e.g. FIG. 123-125), or areleasable friction-fit coupling (e.g. FIG. 126-133).

For example, a frangible release can be implemented in the currentembodiments by a structure attached between an on-skin sensor assembly(e.g. 160), a holder (e.g. 524), a needle carrier (e.g. 508), and/or anapplicator housing (e.g. 502). The frangible component may includefeatures such has a weakened portion or a portion designated to fractureduring release of the on-skin sensor assembly from the applicator.Frangible components configured to fracture may include patch material(e.g. spun lace) or molded components (e.g. ABS, PC, polymer,elastomeric polymer, etc.).

For example, a releasable adhesive can be implemented in the currentembodiments by a releasable adhesive releasably attached between anon-skin sensor assembly (e.g. 160), a holder (e.g. 524), a needlecarrier (e.g. 508), and/or an applicator housing (e.g. 502). Thereleasable adhesive may consist of a double sided adhesive tape, a glue,or a hot melt polymer. The releasable adhesive is configured to detachduring release of the on-skin sensor assembly from the applicator via anapplicator mechanism (e.g. retraction mechanism) or user force.

For example, a releasable friction-fit coupling can be implemented inthe current embodiments by a surface contact between an on-skin sensorassembly (e.g. 160), a holder (e.g. 524), a needle carrier (e.g. 508),and/or an applicator housing (e.g. 502). The releasable friction-fitcoupling may consist of a rigid or elastomeric material (e.g. silicone,TPE, TPU, rubber, etc.) or a combination thereof. The coupled components(e.g. on-skin sensor assembly 160 and holder 524) have a frictionalmaterial interaction (e.g. interference fit, deformable fit, etc.). Thereleasable friction-fit coupling is configured to detach during releaseof the on-skin sensor assembly from the applicator via an applicatormechanism (e.g. retraction mechanism) or user force.

Discussion with respect to FIGS. 71-89 below may be directed to, amongother aspects, applicators that account for skin tenting (e.g., the skinbowing in a substantially convex fashion as the host pushes theapplicator against the skin). FIGS. 71-89 may be further directed topreventing an insertion mechanism, assembly or spring from stalling dueto such skin tenting by, among other aspects, initiating retraction,after insertion, based on an on-skin sensor assembly and/or otherfeatures of the applicator pushing against the skin of the host with aforce sufficient to initiate the retraction, as opposed to retractionbeing triggered by the on-skin sensor assembly and/or other features ofthe applicators reaching a predetermined physical displacement in thedistal direction. It is contemplated that such force-based retractiontrigger allows the transition from insertion to retraction at a varietyof distally displaced positions based at least in part on the locationof the surface of the skin of the host during application.

FIG. 71 illustrates an applicator 7100 for an on-skin sensor assembly ofan analyte sensor system, according to some embodiments. As will bedescribed below, applicator 7100 may comprise an activation element 7104disposed on a side of applicator 7100, for example, on a side of anouter housing 7101 of applicator 7100. In some embodiments, activationelement 7104 may be a button, a switch, a toggle, a slide, a trigger, aknob, a rotating member, a portion of applicator 7100 that deformsand/or flexes or any other suitable mechanism for activating aninsertion and/or retraction assembly of applicator 7100. In someembodiments, activation element 7104 may be disposed in any location,e.g., a top, upper side, lower side, or any other location of applicator7100. Applicator 7100 may be large enough for a host to grasp with ahand and push, or otherwise activate, activation element 7104 with, forexample, a thumb, or with an index finger and/or a middle finger.

Applicator 7100 may be configured with one or more safety features suchthat applicator 7100 is prevented from activating until the safetyfeature is deactivated. In one example, the one or more safety featuresprevents applicator 7100 from activating unless applicator 7100 ispressed against the skin of a host with sufficient force. Moreover, aswill be described in more detail in connection with one or more of FIGS.72-80B below, applicator 7100 may be further configured such that one ormore components therein retract based at least in part on the one ormore components pushing against the skin of the host with a forceexceeding a predetermined threshold, rather than based on the one ormore components translating beyond a predetermined and static distalposition. In other words, applicator 7100 may implement force-basedretraction triggering rather than being limited to displacement-basedretraction triggering.

FIG. 72 illustrates an exploded perspective view of applicator 7100 ofFIG. 71, according to some embodiments. Applicator 7100 may includeouter applicator housing 7101 comprising activation element 7104. Outerapplicator housing 7101 may be configured to translate in a distaldirection by a force applied by a host to applicator 7100, specificallyto inner housing 7102, thereby aligning activation element 7104 in aposition that allows applicator 7100 to fire. Further explanation of thealignment process will be explained below.

Applicator 7100 further comprises inner housing 7102, configured tohouse at least one or more mechanisms utilized to apply on-skin sensorassembly 360 to skin 130 of a host. A distal surface 7130 of a bottomopening of inner housing 7102 may define a bottom surface of applicator7100. In some embodiments, upon pressing applicator 7100 against skin130 of the host, skin 130 may deform in a substantially convex shape atdistal surface 7130 such that at least a portion of a surface of skin130 disposed at the bottom opening of applicator housing 7102 extendsinto the bottom opening of inner housing 7102 beyond a plane defined bydistal surface 7130 in a proximal direction.

In some embodiments, a first barrier layer 7192 may be disposed over oneor more apertures in inner housing 7102, for example, an aperture 7106through which at least a portion of activation element 7104 may beconfigured to extend through during activation of applicator 7100. Insuch embodiments, a portion of activation element 7104 may be configuredto pierce or deform first barrier layer 7192 upon activation ofapplicator 7100. First barrier layer 7192 may comprise a gas permeablematerial such as Tyvek, or a non-gas permeable material such as metallicfoil, polymer film, elastomer, or any other suitable material.

Applicator 7100 may further comprise a needle carrier assembly 7108,including a needle hub 7150 configured to couple an insertion element7174 to needle carrier assembly 7108. In some other embodiments,insertion element 7174 may be directly coupled to needle carrierassembly 7108. Insertion element 7174 is configured to insert sensor 338of on-skin sensor assembly 360 (see FIGS. 3A-4) into skin 130 of thehost (e.g., FIG. 1). In some embodiments, the insertion elementcomprises a needle, for example, an open sided-needle, a needle with adeflected-tip, a curved needle, a polymer-coated needle, a hypodermicneedle, or any other suitable type of needle or structure, as describedin connection with at least FIGS. 47-50 and 80A-B. In yet otherembodiments, insertion element 7174 may be integrally formed with sensor338 and may be sufficiently rigid to be inserted partially into skin 130of the host with minimal or no structural support.

Applicator 7100 may further include a holder 7124 releasably coupled toneedle carrier assembly 7108 and configured to guide needle carrierassembly 7108 and on-skin sensor assembly 360 while coupled to needlecarrier assembly 7108, e.g., at least during translation from a proximalposition to a distal insertion position. As will be described in moredetail below, on-skin sensor assembly 360 may be stripped or releasedfrom holder 7124 and/or needle carrier assembly 7108 once on-skin sensorassembly 360 is disposed on skin 130 of the host.

Applicator 7100 may further comprise an insertion assembly configured totranslate insertion element 7174, needle hub 7150, needle carrierassembly 7108, and on-skin sensor assembly 360 from a proximal position,in the distal direction, to a distal insertion position. Such aninsertion assembly may include a first spring 7112. First spring 7112may be a compression spring, or any suitable type of spring, and mayhave a first end in contact with or coupled to inner applicator housing7102 and a second end in contact with or coupled to holder 7124. Firstspring 7112 is configured to, upon activation of the insertion assembly,translate holder 7124, needle carrier assembly 7108, needle hub 7150,insertion element 7174 and on-skin sensor assembly 360, in the distaldirection to the distal insertion position. Substantially at the distalinsertion position, needle carrier assembly 7108 may decouple fromholder 7124 and on-skin sensor assembly 360.

Applicator 7100 may further comprise a retraction assembly configured totranslate needle carrier assembly 7108, needle hub 7150 and insertionelement 7174, in the proximal direction, from the distal insertionposition to a proximal retracted position. In some embodiments theinitial proximal position may be the same as the proximal retractedposition. In other embodiments, the initial proximal position may bedifferent from the proximal retracted position. Such a retractionassembly may include a second spring 7128. Second spring 7128 may be acompression spring, or any suitable type of spring, and may have a firstend contacting or coupled to holder 7124 and a second end in contactwith or coupled to at least one spring retention element (e.g., 7442 a,7442 b in FIGS. 74A-75B), at least until retraction. Second spring 7128is configured to translate needle carrier assembly 7108, needle hub7150, and insertion element 7174 in the proximal direction from thedistal insertion position to the proximal retracted position in responseto on-skin sensor assembly 360 contacting skin 130 of the host, and/orreaching a limit of travel with a force exceeding a predeterminedthreshold sufficient to cause first end of second spring 7128 toovercome the at least one spring retention element (e.g., 7442 a, 7442 bin FIGS. 74A-75B). In some embodiments, a stop feature (not shown) maybe disposed at a bottom of applicator 7100, e.g., on a distal portion ofinner housing 7102. Such a stop feature may be configured to contact oneor more of on-skin sensor assembly 360, needle carrier 7108, or holder7124 in the distal insertion position.

In some embodiments, transfer of on-skin sensor assembly 360 betweeninsertion and retraction may occur as previously described in connectionwith, for example, any of FIGS. 35A-37C.

In some embodiments, a second barrier layer 7194 may be disposed overthe bottom opening of inner housing 7102. Second barrier layer 7194 maycomprise a gas permeable material such as Tyvek, or a non-gas permeablematerial such as metallic foil, film. In some embodiments, secondbarrier layer 7194 may be removed by the host prior to use of applicator7100. In embodiments comprising one or both of first and second barrierlayers 7192, 7194, such layers may provide a sterile environment betweenapplicator 7100 and the outside environment and/or may allow ingress andegress of gas such as during sterilization.

Although not shown in FIGS. 71-72, in some embodiments, applicator 7100may comprise a cap configured to be secured to distal surface 7130 ofinner housing 7102 and that may be removed before use. In someembodiments, such a cap may also function as a sterile barrier, aspreviously described in U.S. patent application Ser. No. 16/011,527,hereby incorporated by reference in its entirety.

A brief description of some aspects of the operation of applicator 7100follows with respect to FIGS. 73A-73C, which illustrate severalcross-sectional views of applicator 7100 of FIGS. 71 and 72 duringoperation, according to some embodiments. FIGS. 73A-73C may correspondto applicator 7100 cut along the section line A-A′ shown in FIG. 71, forexample.

FIG. 73A illustrates a state of applicator 7100 prior to activation.Holder 7124 comprises an insertion assembly retention element 7332configured to contact inner housing 7102, thereby immobilizing holder7124, needle carrier assembly 7108, needle hub 7150, insertion element7174 and on-skin sensor assembly 360, in the pre-activated state.

Needle carrier assembly 7108 comprises a plurality of wearable retentionand/or alignment elements 7372 a, 7372 b configured to extend throughholder 7124 and releasably couple on-skin sensor assembly 360 to holder7124 and/or to needle carrier assembly 7108. Wearable retention elements7372 a, 7372 b may comprise, e.g., arms, deflection element, tabs,detents, snaps or any other features capable of a retaining function. Insome embodiments, wearable retention elements 7372 a, 7372 b may extendaround rather than through holder 7124. Although two wearable retentionelements are illustrated, any number of wearable retention elements arecontemplated. In some embodiments, wearable retention element(s) 7372 a,7372 b may comprise snap fits, friction fits, interference features,elastomeric grips and/or adhesives configured to couple on-skin sensorassembly 360 with needle carrier assembly 7108 and/or holder 7124.

Inner housing 7102 may comprise a spring 7320 configured to contactouter housing 7101 and maintain a predetermined spacing between outerhousing 7101 and inner housing 7102 in the pre-activation orientation ofFIG. 73A. Spring 7320 may be a compression spring, leaf spring, flex armspring, a piece of foam or rubber, etc. In some other embodiments, outerhousing 7101 may comprise spring 7320 and spring 7320 may be configuredto contact inner housing 7102, in a reverse fashion from that shown inFIG. 73A.

Activation of applicator 7100 may include a host pressing applicator7100 against their skin with sufficient force to translate outer housing7101 in a distal direction, as shown by arrow 7302, toward and withrespect to inner housing 7102 until activation element 7104 is alignedwith aperture 7106 of inner housing 7102 and insertion assemblyretention element 7332 of holder 7124. Insertion assembly retentionelement 7332 may comprise, e.g., an arm, a deflection element, a tab, adetent, a snap or any other feature capable of a retaining function.Once such an alignment is achieved, a host may initiate (e.g. pushing)activation element 7104, as shown by arrow 7304, thereby deflectinginsertion assembly retention element 7332 sufficiently to release holder7124 from inner housing 7102. In some other embodiments, applicator 7100may be configured such that activation element 7104 may be activatedfirst, but that actual insertion is not triggered until outer housing7101 is translated sufficiently in the distal direction toward and withrespect to inner housing 7102. In yet other embodiments, activationelement 7104 may be biased toward a center of applicator 7100 such thatactivation element 7104 need not be explicitly activated by the hostbut, instead, activation element 7104 may be configured to automaticallyinitiate insertion upon outer housing 7101 being translated sufficientlyin the distal direction toward and with respect to inner housing 7102.

Such configurations provide several benefits. First, translation ofouter housing 7101 with respect to inner housing 7102 before activationprovides a measure of drop protection such that if applicator 7100 isaccidentally dropped, it may not prematurely fire. Second, spring 7320provides a force bias that the host has to affirmatively overcome bypressing applicator 7100 into their skin prior to firing, therebyreducing the probability of activating applicator 7100 before it isproperly positioned. Further, the host may decide to not fire applicator7100 and discontinue pressing applicator 7100 against their skin, inwhich spring 7320 will bias against outer housing 7101 and allow outerhousing 7101 to return to its initial state.

Holder 7124, needle carrier assembly 7108, needle hub 7150, insertionelement 7174, on-skin sensor assembly 360, first spring 7112 and secondspring 7128 are all shown in pre-activation positions in FIG. 73A.

FIG. 73B illustrates applicator 7100 during insertion of on-skin sensorassembly 360 but before retraction of needle carrier assembly 7108.First spring 7112 drives holder 7124, needle carrier assembly 7108,needle hub 7150, insertion element 7174, and on-skin sensor assembly360, in the distal direction toward the distal insertion position. FIG.73B illustrates a position where on-skin sensor assembly 360 is incontact with skin 130 of the host but where holder 7124 is not yet fullydriven, by first spring 7112, into contact with on-skin sensor assembly360 or skin 130 of the host.

In some embodiments, masses of each of holder 7124, needle carrierassembly 7108, needle hub 7150, insertion element 7174, and on-skinsensor assembly 360 may be specifically designed to reduce orsubstantially eliminate a tendency of needle carrier assembly 7108,needle hub 7150, insertion element 7174, and on-skin sensor assembly 360to detach due to inertial forces from holder 7124 while being driven inthe distal direction during insertion. In some embodiments, a forceexerted by first spring 7112 may be selected to be sufficient for properoperation of applicator 7100, while not so large as to furtherexacerbate such above-described inertially triggered detachment. In someembodiments, a spring (not shown) may be configured to exert a forceagainst a portion of needle carrier assembly 7108, for example in adistal direction, sufficient to prevent needle carrier assembly 7108from inertially triggered detaching from holder 7124 during insertion.

FIG. 73C illustrates applicator 7100 during activation, as needlecarrier assembly 7108, needle hub 7150 and insertion element 7174 areretracted in the proximal direction by second spring 7128. In FIG. 73C,first spring 7112 has fully driven on-skin sensor assembly 360 to theskin of the host. In this position, second spring 7128 is released fromspring retention elements (e.g., 7442 a, 7442 b in FIGS. 74A-75B) anddrives needle carrier assembly 7108, needle hub 7150, and insertionelement 7174 in the proximal direction from the distal insertionposition. Upon needle carrier assembly 7108 reaching the proximalretraction position, needle carrier retention element 7334 of holder7124 engages with needle carrier assembly 7108, thereby maintainingneedle carrier assembly 7108, needle hub 7150 and insertion element 7174in a locked, retracted position limiting access to insertion element7174. Needle carrier retention element 7334 may comprise, e.g., an arm,a deflection element, a tab, a detent, a snap or any other featurecapable of a retaining function. In this retracted position, needlecarrier assembly 7108, needle hub 7150, and insertion element 7174 isprevented from travelling in a distal direction.

A further description of some aspects of the operation of applicator7100 follows with respect to FIGS. 74A-74C, which illustrate severalcross-sectional views of applicator 7100 of FIGS. 71 and 72 duringoperation, according to some embodiments. FIGS. 74A-74C may correspondto applicator 7100 cut along the section line B-B′ shown in FIG. 71, forexample. For ease of illustration, needle hub 7150 and insertion element7174 are not shown in FIGS. 74A-74C.

FIG. 74A illustrates a state of applicator 7100 prior to activation. Forease of illustration, on-skin sensor assembly 360 is not illustrated inFIG. 74A. Holder 7124 comprises spring retention elements 7442 a, 7442 bconfigured to contact and retain a first end of second spring 7128 inthe pre-activated state, e.g., during insertion, while a second end ofspring 7128 is in contact with needle carrier assembly 7108. Springretention elements 7442 a, 7442 b may comprise, e.g., arms, deflectionelement, tabs, detents, snaps or any other features capable of aretaining function. Although two spring retention elements 7442 a, 7442b are shown, at least one spring retention element is contemplated. Insome embodiments, applicator 7100 may include one spring retentionelement, as shown in FIGS. 81A-81D. In some embodiments, applicator 7100may include three spring retention elements. In some embodiments,applicator 7100 may include four spring retention elements. In someembodiments, spring retention elements 7442 a, 7442 b are deflectablearms, rigid arms, deformable features, snaps, catches, or hooks. In someembodiments, spring retention elements 7442 a, 7442 b may be activelydeflected by one or more features within applicator 7100.

Needle carrier assembly 7108 comprises backstop features 7444 a, 7444 b,configured to prevent lateral deflection of spring retention elements7442 a, 7442 b in the proximal starting position, e.g., at least duringinsertion, thereby supporting retention of second spring 7128 betweenspring retention elements 7442 a, 7442 b and holder 7124 untilretraction. Although two backstop features are illustrated, any numberof backstop features are contemplated. The number of backstop featuresmay equal the number of spring retention elements.

FIG. 75A illustrates a magnified view of spring retention element 7442 band backstop feature 7444 b. In FIG. 75A, first spring 7112 is drivingholder 7124, needle carrier assembly 7108 and on-skin sensor assembly360, in the distal direction toward the distal inserted position.Backstop feature 7444 b is shown engaged to spring retention element7442 b, preventing spring retention element 7442 b from deflectinglaterally, thereby preventing second spring 7128 from releasing. Asshown in FIG. 75A, a proximal end of spring retention element 7442 b maybe offset from a distal end of backstop feature 7444 b by a distance a.In some embodiments, distance a is the length required for springretention element 7442 b to traverse along backstop feature 7444 b suchthat spring retention element 7442 b clears past backstop feature 7444b. Backstop feature 7444 b may feature a ramp to guide spring retentionelement 7442 b. A distal end of needle carrier assembly 7108 and adistal end of holder 7124 may be offset from each other at least thesame distance a to allow for spring retention element 7442 b to traversedistally past backstop feature 7444 b.

It may be appreciated that the frictional force between correspondingcontacting surfaces of backstop feature 7444 b and spring retentionelement 7442 b may at least partly determine an amount of force torelease spring retention element 7442 b from backstop feature 7444 b.This force may allow for lateral deflection of spring retention element7442 b and thus allow the expansion of second spring 7128. In someembodiments, the amount of force is at least 0.1 pounds. In someembodiments, the amount of force is at least 0.5 pounds. In someembodiments, the amount of force is at least 1 pound. In someembodiments, the amount of force is at least 2 pounds. In someembodiments, the amount of force is at least 3 pounds. In someembodiments, the amount of force is at least 4 pounds. In someembodiments, the amount of force is at least 5 pounds.

Although the figure shows backstop feature 7444 b preventing lateraldeflection of spring retention element 7442 b in a radially outwarddirection, it is contemplated that an inverse structural relationshipcan be achieved. For instance, the ramped surface of spring retentionelement 7442 b can be reversed to face the opposite direction as shownin FIG. 75A. Further, the ramped surface of spring retention element7442 b may be biased in a radially inward direction by second spring7128 against backstop feature 7444 b. In such embodiments, backstopfeature 7444 b may be located radially inward of spring retentionelement 7442 b.

Accordingly, in some embodiments, materials utilized to form holder 7124and needle carrier assembly 7108 may be selected based on a desiredamount of force to release spring retention element 7442 b for lateraldeflection. Examples of such materials may include Polycarbonate, ABS,PC/ABS, Polypropylene, HIPS (High impact polystyrene), PolybutyleneTerephthalate (PBT), Polyoxymethylene (POM), Acetal, polyacetal,polyformaldehyde, PTFE, High density polyethylene (HDPE), Nylon,Polyethylene terephthalate (PET), Thermoplastic elastomer (TPE),Thermoplastic polyurethane (TPU), TPSiv, Cyclo olefin polymer (COP),Cyclo olefin copolymer (COC), and/or Liquid-crystal polymer (LCP).

An angle θ of a portion of spring retention element 7442 b in contactwith second spring 7128 may also affect the amount of frictional forceto laterally deflect spring retention element 7442 b and so to releasesecond spring 7128. Accordingly, the angle θ may be selected based on adesired amount of force to laterally deflect spring retention element7442 b sufficiently to release second spring 7128. In some embodiments,the angle θ is at least 1 degree with respect to a vertical axis of thespring retention element 7442 b. In some embodiments, the angle θ is atleast 5 degrees. In some embodiments, the angle θ is at least 10degrees. In some embodiments, the angle θ is at least 15 degrees. Insome embodiments, the angle θ is at least 20 degrees. In someembodiments, the angle θ is about 30 to 45 degrees. In addition, theforce profile of second spring 7128 may affect a target amount offrictional force to laterally deflect spring retention element 7442 b.Accordingly, in some embodiments, the force profile of second spring7128 may be taken into account when selecting one or both of thematerials for forming holder 7124 and needle carrier assembly 7108 andthe angle θ of the portion of spring retention element 7442 b in contactwith second spring 7128.

An angle β of spring retention element 7442 b with respect to a verticalaxis may also affect the amount of frictional force to laterally deflectspring retention element 7442 b and so to release second spring 7128. Bycontacting spring retention element 7442 b, second spring 7128 may exerta force on spring retention element 7442 b at a distance d from a bottomof spring retention element 7442 b that causes a torque momentsufficient to induce a lateral deflection of spring retention element7442 b.

FIG. 75A further illustrates needle carrier assembly 7108 comprising adeflecting element 7522 configured to contact spring retention element7442 b and maintain spring retention element 7442 b in a laterallydeflected orientation once second spring 7128 has initially deflectedspring retention element 7442 b and sufficiently driven needle carrierassembly 7108 in the proximal direction, as will be shown in more detailin FIG. 75B. Deflecting element 7522 may prevent spring retentionelement 7442 b from contacting the windings of second spring 7128 whilesecond spring 7128 is extending, smoothing the operation of applicator7100 and preventing energy released by second spring 7128 and designedfor driving needle carrier assembly 7128 in the proximal direction frombeing absorbed by undesired contact with spring retention element 7442 bduring the release of second spring 7128.

In some embodiments, the angle θ of the portion of spring retentionelement 7442 b in contact with second spring 7128 may be substantially90° (e.g., flat) and deflecting element 7522 may have a ramped or angledsurface in contact with spring retention element 7442 b in the positionillustrated in FIG. 75A. In such embodiments, deflecting element 7522,in addition to the above-described functionality, may be configured toinitially deflect spring retention element 7442 b as first spring 7112drives holder 7124 from the position illustrated in FIG. 75A to theposition illustrated in FIG. 75B.

In some embodiments, inner housing 7102 may comprise a protrusion 7546extending from inner housing 7102 in the distal direction. Protrusion7546 may be configured to contact at least one of spring retentionelements 7442 a, 7442 b and backstop features 7444 a, 7444 b in thepre-activation state such that spring retention elements 7442 a, 7442 bare prevented from laterally deflecting until holder 7124 and needlecarrier assembly 7108 have translated at least a predetermined minimumdistance in the distal direction. Accordingly, protrusion 7546 mayprovide a measure of drop protection such that applicator 7100 may notprematurely fire in response to a concussive shock from being droppedbefore intentional activation.

Turning back to FIG. 74A, inner housing 7102 may further comprise anengagement element 7448 configured to engage with a protrusion 7449 ofneedle carrier assembly 7108 upon needle carrier assembly 7108translating in the distal direction beyond a predetermined threshold,thereby preventing needle carrier assembly 7108 from translating in thedistal direction beyond the predetermined threshold. It is contemplatedthat this may ensure needle carrier assembly retraction in the event ofan air firing or dry firing in which applicator 7100 is somehowactivated when not held against the skin of the host. In someembodiments, the predetermined threshold may correspond to the distalend of needle carrier assembly 7108 extending beyond a point proximal tothe distal end of inner housing 7102, to a point substantially in linewith the distal end of inner housing 7102 or to a point distal of thedistal end of inner housing 7102. In some embodiments, engagementelement 7448 comprises a hook, a U-shaped structure, a loop, aprotrusion, or any other structure capable of engaging with protrusion7449 as described above.

FIG. 74B illustrates applicator 7100 after activation, at a beginning ofa force retraction feature process at or near the distal insertionposition where on-skin sensor assembly 360 may be in contact with theskin of the host. First spring 7112 has driven holder 7124, needlecarrier assembly 7108, needle hub 7150, insertion element, and on-skinsensor assembly 360, in the distal direction toward the distal insertionposition. During proper operation, holder 7124 and on-skin sensorassembly 360 should be pressing against the skin of the host. However,FIG. 74B may also illustrate a dry fire condition, where applicator 7100is not properly pressed against the skin of the host before triggeringapplicator 7100. Accordingly, upon first spring 7112 driving holder 7124and needle carrier assembly 7108 in the distal direction beyond thepredetermined threshold, engagement element 7448 contacts protrusion7449, which prevents needle carrier assembly 7108 from traveling furtherin the distal direction, while holder 7124 is driven sufficientlyfurther in the distal direction such that backstop features 7444 a, 7444b of needle carrier assembly 7108 no longer contact spring retentionelements 7442 a, 7442 b in the distal insertion position, therebyreleasing the first end of second spring 7128 and initiating retractioneven when applicator 7100 is dry fired. The insertion force provided byfirst spring 7112 may be sufficient to additionally overcome thefrictional force between corresponding contacting surfaces of backstopfeature 7444 b and spring retention element 7442 b.

Turning to FIG. 75B, first spring 7112 has driven holder 7124, needlecarrier assembly 7108 and on-skin sensor assembly 360 in the distaldirection to the skin of the host. As first spring 7112 drives holder7124, needle carrier assembly 7108 and on-skin sensor assembly 360against the skin of the host, the skin provides a counter force to theforce generated by first spring 7112. The skin may oppose the force offirst spring 7112 and bias against the distal end of on-skin sensorassembly 360. Because the distal end of holder 7124 is offset from thedistal end of on-skin sensor assembly 360 as shown in FIG. 75A, thecounter force provided by the skin is transferred to holder 7124 asfirst spring 7112 continues to drive holder 7124 towards the skin whileon-skin sensor assembly 360 is pressed against the skin. The counterforce provided by the skin allows spring retention element 7442 b todisplace past backstop feature 7444 b. Once spring retention element7442 b has cleared distance a past backstop feature 7444 b, secondspring 7128 can laterally deflect spring retention element 7442 b,thereby releasing second spring 7128, which drives needle carrierassembly 7108 in the proximal direction. Alternatively, as describedabove in connection with FIG. 75A, where the angle θ of the portion ofspring retention element 7442 b in contact with second spring 7128 issubstantially 90° (e.g., flat), the ramped or angled surface ofdeflecting element 7522 in contact with spring retention element 7444 bdeflects spring retention element 7442 b sufficiently to release secondspring 7128, which drives needle carrier assembly 7108 in the proximaldirection.

In some embodiments, engagement element 7448 may engage protrusion 7449even when applicator 7100 is pressed against the skin of a user. In suchembodiments, engagement element 7448 engages protrusion 7449 as firstspring 7112 drives holder 7124, needle carrier assembly 7108, andon-skin sensor assembly 360 against the skin of the host. As explainedabove, engagement element 7448 prevents needle carrier assembly 7108from moving distally when engagement element 7448 engages protrusion7449. This allows spring retention elements 7442 a, 7442 b to separateaway from backstop features 7444 a, 7444 b and allow for release ofsecond spring 7128. The engagement of engagement element 7448 andprotrusion 7449 may add additional force to the counter force providedby the skin, thus increasing the energy needed to overcome thefrictional engagement of spring retention elements 7442 a, 7442 b andbackstop features 7444 a, 7444 b. In some instances, the engagement ofengagement element 7448 and protrusion 7449 provides an immediateimpulse force that converts at least some of the initial energy of firstspring 7112 into energy needed to overcome the frictional engagement ofspring retention elements 7442 a, 7442 b and backstop features 7444 a,7444 b. It is contemplated that such embodiments may benefit users withsoft skin or higher body fat percentage.

Turning back to FIG. 74C, which illustrates applicator 7100 duringactivation, needle carrier assembly 7108 is retracted in the proximaldirection by second spring 7128, as indicated by arrow 7402. In FIG.74C, with backstop features 7444 a, 7444 b no longer immobilizing springretention elements 7442 a, 7442 b, first end of second spring 7128pushes against spring retention elements 7442 a, 7442 b with sufficientforce to deflect spring retention elements 7442 a, 7442 b in the distalinsertion position when on-skin sensor assembly 360 is in contact withskin 130 of the host, allowing second spring 7128 to clear springretention elements 7442 a, 7442 b and drive needle carrier assembly 7108in the proximal direction, thereby maintaining needle carrier assembly7108, needle hub 7150 (see FIGS. 73A-73C) and insertion element 7174(see FIGS. 73A-73C) in a locked, retracted position even in the event ofa dry fire.

FIGS. 76A and 76B illustrate magnified views of some features of anapplicator, such as applicator 7100, according to some embodiments.

In FIG. 76A, first spring 7112 (see FIGS. 72-74C) is driving holder7124, as well as the needle carrier assembly and on-skin sensor assembly360 in the distal direction, illustrated by arrow 7602, toward thedistal insertion position. Retention element 7372 b of the needlecarrier assembly is releasably coupled to on-skin sensor assembly 360.As illustrated, during insertion and near the distal inserted position,holder 7124 is in contact with spring retention element 7372 b,preventing spring retention element 7372 b from deflecting laterally andthereby rigidly securing on-skin sensor assembly 360 to the needlecarrier assembly.

In FIG. 76B, second spring 7128 (see FIGS. 72-74C) is driving needlecarrier assembly 7108 in the proximal direction from the distalinsertion position. Because holder 7124 has been driven sufficiently inthe distal direction, at the distal insertion position, holder 7124 isno longer in contact with wearable retention element 7372 b.Accordingly, wearable retention element 7372 b is free to deflectlaterally, thereby releasing on-skin sensor assembly 360 from wearableretention element 7372 b and thus from the needle carrier assembly 7108.Needle carrier assembly 7108 is now driven in the proximal direction bysecond spring 7128, while on-skin sensor assembly 360 is secured to theskin of the host. Moreover, in some embodiments, because holder 7124 isdriven to the distal inserted position and substantially held in thatposition by first spring 7112, holder 7124 may press against one or bothof on-skin sensor assembly 360 or an adhesive patch of on-skin sensorassembly 360, supporting one or both during attachment to the skin ofthe host.

FIG. 90 illustrates a magnified view of some features of the applicatorof FIGS. 71 and 72, according to some embodiments. As shown, applicator7100 is in a pre-activation state. In this state, spring retentionelements 7442 a, 7442 b may be retained against backstop features 7444a, 7444 b. Second spring 7128 may be biasing spring retention elements7442 a, 7442 b against backstop features 7444 a, 7444 b. As describedabove, sufficient force is needed to deflect spring retention elements7442 a, 7442 b past backstop features 7444 a, 7444 b. The sufficientforce may be determined or at least partly determined by the frictionalforce between spring retention elements 7442 a, 7442 b and backstopfeatures 7444 a, 7444 b. It may be appreciated that backstop features7444 a and 7444 b may feature a groove 7446 a and a groove 7446 b,respectively, to engage with spring retention elements 7442 a, 7442 b.Grooves 7446 a, 7446 b may increase a drag force between springretention elements 7442 a, 7442 b and backstop features 7444 a, 7444 b.In such embodiments, grooves 7446 a, 7446 b can increase the forcerequired to deflect spring retention elements 7442 a, 7442 b frombackstop features 7444 a, 7444 b while the materials of spring retentionelements 7442 a, 7442 b and/or backstop features 7444 a, 7444 b have lowor lower coefficient of friction. Further, grooves 7446 a, 7446 b canincrease the force required to deflect spring retention elements 7442 a,7442 b from backstop features 7444 a, 7444 b while second spring 7128has a small or smaller diameter or has a low or lower spring constant.In some embodiments, grooves 7446 a, 7446 b may each feature a concavechannel. The concave shape of the channel may feature angled surfacesconfigured to drag against multiple edges of spring retention elements7442 a, 7442 b. In such embodiments, spring retention element 7442 a,7442 b can be wedges configured to drag within grooves 7446 a, 7446 b.In some embodiments, applicator 7100 may include as many grooves 7446 asbackstop features 7444.

FIG. 77 illustrates a perspective partial cutaway view of needle carrierassembly 7108, needle hub 7150, and on-skin sensor assembly 360 ofapplicator 7100 of FIGS. 71 and 72, according to some embodiments. FIG.78 illustrates a cross-sectional view of needle hub 7150 and on-skinsensor assembly 360, according to some embodiments. FIG. 79 illustratesa top view of a portion of needle carrier assembly 7108 and needle hub7150, according to some embodiments. The following is a description ofthese features with reference to FIGS. 77-79.

On-skin sensor assembly 360 comprises sensor assembly aperture 396. Hub7150 is configured to couple insertion element 7174 to needle carrierassembly 7108 and to substantially maintain a desired orientation ofinsertion element 7174 during insertion of the sensor of on-skin sensorassembly 360 into the skin of the host.

Needle hub 7150 comprises a plurality of upper arms 7156 a, 7156 b, aplurality of lower arms 7154 a, 7154 b, and a base 7152. Although twoupper arms and two lower arms are illustrated, any number of arms,including a single upper and lower arm, are contemplated. In someembodiments, upper arms 7156 a, 7156 b and lower arms 7154 a, 7154 b maybe flexible such that, when needle hub 7150 is coupled to needle carrierassembly 7108, upper arms 7156 a, 7156 b and lower arms 7154 a, 7154 bsecure needle hub 7150 in a desired orientation with respect to needlecarrier assembly 7108. For example, upper arms 7156 a, 7156 b may beconfigured to flex radially inward, such that when disposed through acarrier aperture 7712 in needle carrier assembly 7108, upper arms 7156a, 7156 b are in contact with an upper surface of needle carrierassembly 7108 adjacent to carrier aperture 7712 and lower arms 7154 a,7154 b are in contact with a lower surface of needle carrier assembly7108 adjacent to carrier aperture 7712. Such an arrangement allows acompliant fit between needle carrier assembly 7108 and needle hub 7150where lower arms 7154 a, 7154 b deflect to allow upper arms 7156 a, 7156b to expand after clearing surface of carrier aperture 7712. The lowerarms 7154 a, 7154 b can partially or fully relax to bias the needle hubin a distal direction and decrease the clearance between the needle huband the needle carrier that would otherwise exist with a non-compliantfit. In addition, upper arms 7156 a, 7156 b and lower arms 7154 a, 7154b also help to maintain contact between base 7152 and a top surface ofon-skin sensor assembly 360.

Base 7152 comprises an anti-rotation feature. The anti-rotation featuremay comprise a key having a shape complementary to at least a portion ofsensor assembly aperture 396 of on-skin sensor assembly 360 and may beconfigured to substantially prevent needle hub 7150 from rotating aboutan axis 7702 parallel to insertion element 7174 with respect to on-skinsensor assembly 360, e.g., to prevent rotation of base 7152 withinsensor assembly aperture 396. In addition, or the alternative, the uppersurface of needle carrier assembly 7108 adjacent to carrier aperture7712 may comprise a groove 7910 configured to accept upper arms 7156 a,7156 b when upper arms 7156 a, 7156 b are disposed through carrieraperture 7712 in an orientation complementary to an orientation ofgroove 7910, as illustrated in FIG. 79, thereby immobilizing needle hub7150 with respect to needle carrier assembly 7108.

In some embodiments, base 7152 further comprises a substantially flatsurface configured to mate with a top surface of on-skin sensor assembly360 and maintain insertion element 7174 in a substantially perpendicularorientation to the top surface of on-skin sensor assembly 360, in somecases, when the anti-rotation feature of base 7152 is engaged withinsensor assembly aperture 396 of on-skin sensor assembly 360.

Based at least upon the above-described features of needle hub 7150,on-skin sensor assembly 360, and/or needle carrier assembly 7108, base7152 allows easy assembly during manufacture, including but not limitedto proper alignment and preassembly of insertion element 7174 ontoon-skin sensor assembly 360, and/or the ability to easily engage anassembly of needle hub 7150, insertion element 7174, sensor 338 andon-skin sensor assembly 360 to other portions of assembled applicator7100.

FIGS. 80A and 80B illustrate perspective views of locking features forneedles 8074 a, 8074 b for use in an applicator for an analyte sensorsystem, according to some embodiments. For example, needle 8074 a ofFIG. 80A comprises a locking feature comprising a ridge 8076 configuredto mate with a complementary-shaped feature within needle hub 7150, forexample. In the alternative, needle 8074 b of FIG. 80B comprises alocking feature comprising a groove 8078 configured to mate with acomplementary-shaped feature within needle hub 7150, for example.

In yet another alternative, any insertion element described in thisdisclosure may comprise a locking feature that heat stakes the selectedinsertion element to needle hub 7150, for example. In yet anotheralternative, any insertion element described in this disclosure maycomprise a locking feature comprising one or more friction-fit orsnap-fit elements securing the selected insertion element to needle hub7150, for example. In yet another alternative, any insertion elementdescribed in this disclosure may comprise a locking feature comprisingcomplementary clamshell elements on the selected insertion element andneedle hub 7150, for example, configured to mate with one another. Inyet another alternative, any insertion element described in thisdisclosure may comprise a locking element comprising one or moreinserted molded elements configured to couple the selected insertionelement to needle hub 7150, for example.

During manufacture, applicator 7100 may be assembled in stages. Forexample, and not limitation, if present, first barrier layer 7192may beaffixed to inner housing 7102. Insertion element 7174 may be coupled toneedle hub 7150, which may then be coupled to on-skin sensor assembly360. Second spring 7128 may be placed into holder 7124 or needle carrierassembly 7108 and then needle carrier assembly 7108 may be disposed intoholder 7124 and attached to needle hub 7150 and to on-skin sensorassembly 360 via wearable retention elements 7372 a, 7372 b. Firstspring 7112 may be disposed in holder 7124, which may then be installedinto inner housing 7102. Inner housing 7102 may be inserted into andsecured to outer housing 7102. If present, second barrier layer 7194 maybe affixed to inner housing 7102. If a separate element, activationelement 7104 may then be disposed into outer housing 7101. Any labeling,sterilizing and/or packaging may then be applied to applicator 7100.

FIGS. 81A-81C illustrate several cross-sectional views, and variousfeatures and operating positions, of yet another applicator 8100 for anon-skin sensor assembly of an analyte sensor system, according to someembodiments.

Applicator 8100 may include outer applicator housing 7101 comprisingactivation element 7104. Outer applicator housing 7101 may be configuredto translate in a distal direction under force applied by a host ofapplicator 8100, thereby aligning activation element 7104 in a positionthat allows applicator 8100 to fire, an alignment illustrated by FIG.81A. As previously described in connection with applicator 7100, in someembodiments, activation element 7104 may be disposed in any location,e.g., a top, upper side, lower side, or any other location of applicator8100.

Applicator 8100 further comprises inner housing 7102, configured tohouse one or more mechanisms utilized to apply on-skin sensor assembly360 to skin of a host. Distal surface 7130 of a bottom opening of innerhousing 7102 may define a bottom surface of applicator 8100. In someembodiments, upon pressing applicator 8100 against the skin of the host,the skin may deform in a substantially convex shape at distal surface7130 such that at least a portion of a surface of the skin disposed atthe bottom opening of applicator housing 7102 extends into the bottomopening of inner housing 7102, in a proximal direction, beyond a planedefined by distal surface 7130.

Although not illustrated in FIGS. 81A-81C, inner housing 7102 maycomprise a spring 7320 configured to contact outer housing 7101 andmaintain a predetermined spacing between outer housing 7101 and innerhousing 7102 in the pre-activation orientation (see FIG. 73A). Spring7320 may be a compression spring, leaf spring, flex arm spring, a pieceof foam or rubber, etc. In some other embodiments, outer housing 7101may comprise spring 7320 and spring 7320 may be configured to contactinner housing 7102.

Applicator 8100 may further comprise a needle carrier assembly 8108.Needle carrier assembly 8108 comprises wearable retention and/oralignment elements 7372 a, 7372 b configured to pass through holder 8124and releasably couple on-skin sensor assembly 360 to holder 8124 and/orto needle carrier assembly 8108. Although two wearable retention and/oralignment elements are illustrated, any number of wearable retentionand/or alignment elements are contemplated.

Applicator 8100 further comprises needle hub 7150 configured to coupleinsertion element 7174 to needle carrier assembly 8108. Insertionelement 7174 is configured to insert sensor 338 of on-skin sensorassembly 360 into skin 130 of the host (e.g., FIGS. 3A-4). In someembodiments, insertion element 7174 comprises a needle, for example, anopen sided-needle, a needle with a deflected-tip, a curved needle, apolymer-coated needle, a hypodermic needle, or any other suitable typeof needle or structure, as described in connection with at least FIGS.47-50 and 80A-B. In yet other embodiments, insertion element 7174 may beintegrally formed with sensor 338, in which insertion element 7174 maybe sufficiently rigid to be inserted partially into skin 130 of the hostwith minimal or no structural support.

Applicator 8100 may further include holder 8124 releasably coupled toneedle carrier assembly 8108 and configured to guide on-skin sensorassembly 360 while coupled to needle carrier assembly 8108, e.g., atleast during translation from a proximal position to a distal insertionposition. As previously described in connection with applicator 7100,on-skin sensor assembly 360 may be stripped or released from holder 8124and/or needle carrier assembly 8108 once on-skin sensor assembly 360 isdisposed on the skin of the host.

Applicator 8100 may further comprise an insertion assembly configured totranslate insertion element 7174, needle hub 7150, and needle carrierassembly 8108 from a proximal position, in the distal direction, to adistal insertion position. Such an insertion assembly may include firstspring 7112. First spring 7112 may be a compression spring, or anysuitable type of spring, and may have its first end in contact with orcoupled to inner applicator housing 7102 and its second end in contactwith or coupled to holder 8124. First spring 7112 is configured to, uponactivation of the insertion assembly, translate holder 8124, needlecarrier assembly 8108, needle hub 7150, insertion element 7174 andon-skin sensor assembly 360, in the distal direction to the distalinsertion position. Substantially at the distal insertion position,needle carrier assembly 8108 may decouple from holder 8124 and on-skinsensor assembly 360.

Applicator 8100 may further comprise a retraction assembly configured totranslate needle carrier assembly 8108, needle hub 7150 and insertionelement 7174, in the proximal direction, from the distal insertionposition to a proximal retracted position. In some embodiments theinitial proximal position may be the same as the proximal retractedposition. In other embodiments, the initial proximal position may bedifferent from the proximal retracted position. Such a retractionassembly may include a second spring 8128. Second spring 8128 may be acompression spring, or any suitable type of spring, and may have a firstend contacting or coupled to holder 8124 and a second end, comprising atang 8129 (e.g., a spring portion or spring end) disposed substantiallyalong a diameter of second spring 8128, in contact with or coupled to aspring retention element 8142 of holder 8124, at least until retraction.Spring retention element 8142 may comprise, e.g., an arm, a deflectionelement, a tab, a detent, a snap or any other feature capable of aretaining function. Spring retention element 8142 may have substantiallythe same form and function as spring retention elements 7442 a, 7442 bof applicator 7100 except as described below. Second spring 8128 isconfigured to translate needle carrier assembly 8108, needle hub 7150,and insertion element 7174 in the proximal direction from the distalinsertion position to the proximal retracted position. Tang 8129 ofsecond spring 8128 is released from spring retention element 8142 in thedistal insertion position when spring retention element 8142 is notbacked up by backstop element 8144 and in response to tang 8129 ofsecond spring 8128 pushing against spring retention element 8142 with aforce exceeding a predetermined threshold sufficient to overcome anddeflect spring retention element 8142.

In some embodiments, transfer of on-skin sensor assembly 360 betweeninsertion and retraction may occur as previously described in connectionwith, for example, any of FIGS. 35A-37C.

Needle carrier assembly 8108 further comprises a backstop feature 8144,configured to prevent lateral motion of spring retention element 8142 ofholder 8124 in at least the proximal pre-activation position, therebysupporting retention of second spring 8128 between spring retentionelement 8142 and holder 8124 until retraction. In the orientation shownin FIG. 81A, second spring 8128 is exerting a force against springretention element 8142 but backstop feature 8144 prevents lateraldeflection of retention element 8142.

Holder 8124 further comprises needle carrier retention element 7334,which may comprise a deflectable arm, rigid arm, deformable feature,snap, catch, or hook. Upon needle carrier assembly 8108 reaching theproximal retraction position after activation, needle carrier retentionelement 7334 is configured to engage with needle carrier assembly 8108,thereby maintaining needle carrier assembly 8108, needle hub 7150 andinsertion element 7174 in a locked, retracted position, limiting accessto insertion element 7174.

Although not illustrated in FIGS. 81A-81C, inner housing 7102 ofapplicator 8100 may further comprise engagement element 7448 and needlecarrier assembly 8108 may further comprise protrusion 7449 and mayfunction substantially as previously described in connection with atleast FIGS. 74A-74C.

Although not illustrated in FIGS. 81A-81C, inner housing 7102 ofapplicator 8100 may further comprise a protrusion extending from innerhousing 7102 in the distal direction, substantially as previouslydescribed protrusion 7546. Similar to that previously described inconnection with FIG. 75A, this protrusion may be configured to contactat least one of spring retention element 8142 and backstop feature 8144in the pre-activation state such that spring retention element 8142 isprevented from laterally deflecting until holder 8124 and needle carrierassembly 8108 have translated at least a predetermined minimum distancein the distal direction. Accordingly, the protrusion may provide ameasure of drop protection such that applicator 8100 may not prematurelyfire in response to a concussive shock from being dropped beforeactivation.

Applicator 8100 functions substantially similarly to applicator 7100with the exception that instead of utilizing spring retention elements7442 a, 7442 b, which are disposed along an outside of second coil 7128and are configured to contact and retain a coil of second spring 7128,applicator 8100 utilizes spring retention element 8142, which isdisposed along an inside of second spring 8128 and is configured tocontact and retain tang 8129 of second spring 8128 along a diameter ofsecond spring 8128. Disposing spring retention element 8142 within andsubstantially along a center of second spring 8128, as opposed to alongan outside of second spring 8128, further ensures that spring retentionelement 8142 does not contact the coils of second spring 8128 as secondspring 8128 extends during retraction, thereby smoothing the operationof applicator 8100. In addition, the arrangement including springretention element 8142, as opposed to spring retention elements 7442 a,7442 b mitigates the risk of, and difficulty ensuring that, multiplespring retention elements trigger or are overcome at substantially thesame time.

Although not shown in FIGS. 81A-81C, in some embodiments, applicator8100 may comprise a cap configured to be secured to distal surface 7130of inner housing 7102, which may be removed before use. In someembodiments, such a cap may also function as a sterile barrier, aspreviously described in U.S. patent application Ser. No. 16/011,527,hereby incorporated by reference in its entirety.

FIG. 81A illustrates a state of applicator 8100 prior to activation,according to some embodiments. Holder 8124, needle carrier assembly8108, needle hub 7150, insertion element 7174, on-skin sensor assembly360, first spring 7112 and second spring 7128 are all shown inpre-activation positions.

Retention element 7332 of holder 8124 is in contact with inner housing7102, thereby immobilizing holder 8124, and therefore also needlecarrier assembly 8108, needle hub 7150, insertion element 7174 andon-skin sensor assembly 360, in the pre-activated state.

Backstop feature 8144 of needle carrier assembly 8108 is in contact withand prevents spring retention element 8142 from deflecting laterally,thereby ensuring spring retention element 8142 retains tang 8129 ofsecond spring 8128 in the loaded or pre-activation position shown.

Activation of applicator 8100 may include a host pressing applicator8100 against their skin with sufficient force to translate outer housing7101 in a distal direction toward and with respect to inner housing 7102until activation element 7104 is aligned with insertion assemblyretention element 7332 of holder 8124, as shown in FIG. 81A. Once suchan alignment is achieved, a host may initiate activation element 7104,thereby deflecting insertion assembly retention element 7332sufficiently to release holder 8124 from inner housing 7102. In someother embodiments, applicator 8100 may be configured such thatactivation element 7104 may be activated first, but that actualinsertion is not triggered until outer housing 7101 is translatedsufficiently in the distal direction toward and with respect to innerhousing 7102. In yet other embodiments, activation element 7104 may bebiased toward a center of applicator 8100 such that activation element7104 need not be explicitly activated by the host but, instead,activation element 7104 may be configured to automatically initiateinsertion upon outer housing 7101 being translated sufficiently in thedistal direction toward and with respect to inner housing 7102.

FIG. 81B illustrates applicator 8100 after activation and duringinsertion, according to some embodiments. First spring 7112 drivesholder 8124, and so needle carrier assembly 8108, needle hub 7150,insertion element 7174, and on-skin sensor assembly 360, in the distaldirection toward the distal insertion position. FIG. 81B illustrateson-skin sensor assembly 360 in contact with skin 130 of the host butwhere holder 8124 is not yet fully driven, by first spring 7112, intocontact with on-skin sensor assembly 360 or skin 130 of the host.

In some embodiments, masses of each of holder 8124, needle carrierassembly 8108, needle hub 7150, insertion element 7174, and on-skinsensor assembly 360 may be specifically designed to reduce orsubstantially eliminate a tendency of needle carrier assembly 8108,needle hub 7150, insertion element 7174, and on-skin sensor assembly 360to detach from holder 8124 while being driven in the distal directionduring insertion. In some embodiments, a force exerted by first spring7112 may further be selected to be sufficient for proper operation ofapplicator 7100, while not so large as to further exacerbate suchabove-described inertially triggered detachment. In some embodiments, aspring (not shown) may be configured to exert a force against a portionof needle carrier assembly 8108, for example in the distal direction,sufficient to prevent needle carrier assembly 7108 from inertiallytriggered detaching from holder 8124 during insertion.

FIG. 81C illustrates applicator 8100 after activation and at or near thedistal insertion position, according to some embodiments. First spring7112 has driven holder 8124, needle carrier assembly 8108 and on-skinsensor assembly 360 in the distal direction to the distal insertedposition. Since first spring 7112 has driven holder 8124 a shortdistance farther in the distal direction than needle carrier assembly8108, backstop feature 8144 is no longer in contact with springretention element 8142, allowing second spring 8128 (e.g. tang 8129) tolaterally deflect spring retention element 8142, thereby releasingsecond spring 8128, which drives needle carrier assembly 8108 in theproximal direction. Alternatively, similar to that described above inconnection with applicator 7100 in FIG. 75A, where the angle θ of theportion of spring retention element 8142 in contact with tang 8129 ofsecond spring 7128 is substantially 90° (e.g., flat), spring retentionelement 8142 may be biased to automatically deflect sufficiently torelease second spring 7128 once backstop feature 8144 is no longer incontact with spring retention element 8142, thereby freeing secondspring 8128 to drive needle carrier assembly 8108 in the proximaldirection. Although not shown in FIGS. 81A-81C, inner housing 7102 mayfurther comprise engagement element 7448 configured to engage with aprotrusion 7449 of needle carrier assembly 8108, and to functionsubstantially as previously described in connection with at least FIGS.74A-74C. In some embodiments, a stop feature (not shown) may be disposedat a bottom of applicator 8100, e.g., on a distal portion of innerhousing 7102. Such a stop feature may be configured to contact one ormore of on-skin sensor assembly 360, needle carrier 8108, or holder 8124in the distal insertion position.

Upon release of second spring 8128, second spring 8128 is configured todrive needle carrier assembly 8108, needle hub 7150 and insertionelement 7174, in the proximal direction. Although not shown in FIG. 81C,as needle carrier assembly 8108 travels to the proximal retractedposition, needle carrier retention element 7134 may engage with needlecarrier assembly 8108, thereby retention needle carrier assembly 8108,needle hub 7150 and insertion element 7174, in a locked, retractedposition limiting access to insertion element 7174.

FIG. 81D illustrates a perspective view of holder 8124, first spring7112 and second spring 8128 of applicator 8100, according to someembodiments. FIG. 81D illustrates spring retention element 8142,retention tang 8129 of second spring 8128 in an orientation withinapplicator 8100 before retraction.

During manufacture, applicator 8100 may be assembled in stages. Forexample, and not limitation, if present, as previously described inconnection with applicator 7100, first barrier layer 7192 (see FIG. 72)may be affixed to inner housing 7102. Insertion element 7174 may becoupled to needle hub 7150, which may then be coupled to on-skin sensorassembly 360. Second spring may be placed into holder 8124 or needlecarrier assembly 8108 and then needle carrier assembly 8108 may bedisposed into holder 8124 and attached to needle hub 7150 and to on-skinsensor assembly via wearable retention elements 7372 a, 7372 b. Firstspring 7112 may be disposed in holder 8124, which may then be installedinto inner housing 7102. Inner housing 7102 may be inserted into andsecured to outer housing 7102. If present, as previously described inconnection with applicator 7100, second barrier layers 7194 (see FIG.72) may be affixed to inner housing 7102. If a separate element,activation element 7104 may then be disposed into outer housing 7101.Any labeling, sterilizing and/or packaging may then be applied toapplicator 8100.

FIGS. 82A-82D illustrate several cutaway views, and various features andoperating positions, of yet another applicator 8200 for an on-skinsensor assembly of an analyte sensor system, according to someembodiments. In contrast to applicators 7100 and 8100, applicator 8200utilizes a single spring for both insertion and retraction of aninsertion element 8274 for placing an associated sensor 338 and on-skinsensor assembly 360.

Applicator 8200 comprises a housing 8202 and an activation element 8204disposed on a top of applicator 8200. However, activation element 8204may be disposed on a side or any other location on applicator 8200.

Applicator 8200 may further comprise a needle carrier assembly 8208.Needle carrier assembly 8208 comprises wearable retention and/oralignment elements 8272 a, 8272 b configured to pass through holder 8224and releasably couple on-skin sensor assembly 360 to holder 8224 and/orto needle carrier assembly 8208. In some embodiments, wearable retentionelements 8272 a, 8272 b may extend around rather than through holder8224. Wearable retention elements 8272 a, 8272 b may comprise, e.g.,arms, deflection element, tabs, detents, snaps or any other featurescapable of a retaining function. Although two wearable retention and/oralignment elements are illustrated, any number of wearable retentionand/or alignment elements are contemplated. Needle carrier assembly 8208further comprises a protrusion 8266 configured to contact or hook adeployment sleeve 8206 during retraction, thereby causing needle carrierassembly 8208 to translate in a proximal direction during retraction, aswill be described in more detail below.

Applicator 8200 further comprises an insertion element 8274 configuredto insert sensor 338 of on-skin sensor assembly 360 into skin 130 of thehost (e.g., FIG. 1). In some embodiments, insertion element 8274comprises a needle, for example, an open sided-needle, a needle with adeflected-tip, a curved needle, a polymer-coated needle, a hypodermicneedle, or any other suitable type of needle or structure, as describedin connection with at least FIGS. 47-50 and 80A-B. In yet otherembodiments, insertion element 8274 may comprise sensor 338,sufficiently rigid to be inserted partially into skin 130 of the hostwith minimal or no structural support.

Although not illustrated in FIGS. 82A-82D, in some embodiments,applicator 8200 may further comprise needle hub 7150, configured tocouple insertion element 8274 to needle carrier assembly 8208, aspreviously described in connection with at least FIGS. 77-79. In someother embodiments, insertion element 8274 may be directly coupled toneedle carrier assembly 8208 as shown in FIGS. 82A-82D.

Applicator 8200 may further include holder 8224 releasably coupled todeployment sleeve 8206 via holder retention elements 8232 a, 8232 b andto needle carrier assembly 8208. Holder retention elements 8232 a, 8232b may comprise, e.g., arms, deflection elements, tabs, detents, snaps orany other features capable of a retaining function. Holder 8224 isconfigured to guide on-skin sensor assembly 360 while coupled to needlecarrier assembly 8208 during insertion, e.g., at least duringtranslation from a proximal position to a distal insertion position. Aspreviously described in connection with applicators 7100 and 8100,on-skin sensor assembly 360 may be stripped or released from holder 8224and/or needle carrier assembly 8208 once on-skin sensor assembly 360 isdisposed on the skin of the host.

Applicator 8200 may further comprise an insertion assembly configured totranslate holder 8224, insertion element 8274 and needle carrierassembly 8208, in the distal direction, from a proximal position to adistal insertion position. Such an insertion assembly may include aspring 8212. First spring 8212 may be a compression spring, or anysuitable type of spring, and may have a first end in contact with orcoupled to deployment sleeve 8206 and a second end in contact with orcoupled to holder 8224. First spring 8212 is configured to, uponactivation of the insertion assembly, translate holder 8224, needlecarrier assembly 8208, insertion element 8274 and on-skin sensorassembly 360 in the distal direction to the distal insertion position.Substantially at the distal insertion position, needle carrier assembly8208 may decouple from holder 8224 and on-skin sensor assembly 360.

Applicator 8200 may further comprise a retraction assembly configured totranslate needle carrier assembly 8208 and insertion element 8274, inthe proximal direction, from the distal insertion position to a proximalretracted position. In some embodiments the initial proximal positionmay be the same as the proximal retracted position. In otherembodiments, the initial proximal position may be different from theproximal retracted position. Such a retraction assembly may also includespring 8212. First spring 8212 is also configured to translatedeployment sleeve 8206, needle carrier assembly 8208 and insertionelement 8274 in the proximal direction from the distal insertionposition to the proximal retracted position in response to on-skinsensor assembly 360 contacting skin 130 of the host and/or reaching alimit of travel with a force exceeding a predetermined threshold. Forexample, although not illustrated, housing 8202 may further compriseengagement element 7448 configured to engage with a protrusion 7449 ofneedle carrier assembly 8208, and to function substantially aspreviously described in connection with at least FIGS. 74A-74C. In someembodiments, a stop feature (not shown) may be disposed at a bottom ofapplicator 8200, e.g., on a distal portion of housing 8202. Such a stopfeature may be configured to contact one or more of on-skin sensorassembly 360, needle carrier 8208, holder 8224 or deployment sleeve 8206in the distal insertion position. Spring 8212 is configured to exert aforce sufficient to deflect deployment sleeve retention elements 8262 a,8262 b of deployment sleeve 8206 when on-skin sensor assembly 360 is incontact with skin 130 of the host, thereby freeing deployment sleeveretention elements 8262 a, 8262 b of deployment sleeve 8206 fromprotrusions 8264 a, 8264 b of housing 8202 (see FIGS. 82C-82D), therebyallowing spring 8212 to translate deployment sleeve 8206, and thusneedle carrier assembly 8208 and insertion element 8274, in the proximaldirection from the distal inserted position. Deployment sleeve retentionelements 8262 a, 8262 b may comprise, e.g., arms, deflection elements,tabs, detents, snaps or any other features capable of a retainingfunction.

In some embodiments, transfer of on-skin sensor assembly 360 betweeninsertion and retraction may occur as previously described in connectionwith any prior figure, for example, any of FIGS. 35A-37C.

Such dual insertion/retraction operability of spring 8212 is possiblebecause, during insertion, deployment sleeve 8206 is immobilized bydeployment sleeve retention elements 8262 a, 8262 b, being in contactwith respective protrusions 8264 a, 8264 b of housing 8202. Thus, whenspring 8212 exerts force between deployment sleeve 8206 and holder 8224,spring 8212 drives holder 8224, and coupled needle carrier assembly8208, insertion element 8274 and on-skin sensor assembly 360, in thedistal direction to the distal deployed position, where on-skin sensorassembly 360 is in contact with the skin 130 of the host. Once on-skinsensor assembly 360 is in contact with the host, holder 8224 isimmobilized against on-skin sensor assembly 360, a travel-limitingfeature of applicator 8200, and/or the skin of the host. Accordingly,with holder 8224 immobilized, the force exerted by spring 8212 betweenimmobilized holder 8224 and deployment sleeve 8206 now acts to pushdeployment sleeve 8206 in the proximal direction with sufficient forceto deflect deployment sleeve retention elements 8262 a, 8262 bsufficiently to clear protrusions 8264 a, 8264 b of housing 8202,thereby freeing deployment sleeve 8206 to be driven further in theproximal direction by spring 8212. Since protrusion 8266 of needlecarrier assembly 8208 is configured to contact, couple or hookdeployment sleeve 8206 as deployment sleeve 8206 translates in theproximal direction, the action of spring 8212 translating deploymentsleeve 8206 in the proximal direction also translates needle carrierassembly 8208, and coupled insertion element 8274, in the proximaldirection to the proximal retracted position. Positions of theabove-described features will now be discussed with respect to FIGS.82A-82D.

Although not shown in FIGS. 82A-82D, in some embodiments, applicator8200 may comprise a cap configured to be secured to a distal surface ofinner housing 8202 or activation element 8204, which may be removedbefore use. In some embodiments, this cap may create a sealed volumethat provides a sterile barrier, as previously described in U.S. patentapplication Ser. No. 16/011,527, hereby incorporated by reference in itsentirety.

FIG. 82A illustrates a state of applicator 8200 prior to activation,according to some embodiments. Prior to activation, holder retentionelements 8232 a, 8232 b immobilize holder 8224 to deployment sleeve8206. Holder retention elements 8232 a, 8232 b may comprise, e.g., arms,deflection elements, tabs, detents, snaps or any other features capableof a retaining function. Needle carrier assembly 8208 is coupled toholder 8224. Insertion element 8274 is coupled to needle carrierassembly 8208. And on-skin sensor assembly 360 is coupled to needlecarrier assembly 8208 via wearable retention elements 8272 a, 8272 b.The positions illustrated may correspond to the proximal position.

FIG. 82B illustrates a state of applicator 8200 at activation, accordingto some embodiments. Activation element 8204 is shown as activated(e.g., pressed down) such that protrusions 8264 a, 8264 b translate inthe distal direction sufficiently to laterally deflect holder retentionelements 8232 a, 8232 b, thereby decoupling holder 8224 from deploymentsleeve 8206 and freeing spring 8212 to drive holder 8224, needle carrierassembly 8208, insertion element 8274 and on-skin sensor assembly 360.As in FIG. 82A, the illustrated positions of deployment sleeve 8206,holder 8224, needle carrier assembly 8208, insertion element 8274 andon-skin sensor assembly 360 may correspond to the initial proximalposition.

FIG. 82C illustrates a state of applicator 8200 at the end of insertion,according to some embodiments. First spring 8212 has translated holder8224, needle carrier assembly 8208, insertion element 8274 and on-skinsensor assembly 360 in the distal direction to the distal insertionposition. On-skin sensor assembly 360 is shown in contact with skin 130of the host, insertion element 8274 is inserted into skin 130 of thehost, and holder 8224 is being pressed against on-skin sensor assembly360 by spring 8212. In the illustrated positions, spring 8212 isexerting a force on deployment sleeve 8206 sufficient to laterallydeflect deployment sleeve retention elements 8262 a, 8262 b, therebyfreeing deployment sleeve 8206 to be translated in the proximaldirection by spring 8212. The illustrated positions of holder 8224,needle carrier assembly 8208, insertion element 8274 and on-skin sensorassembly 360 may correspond to the distal inserted position.

In some embodiments, masses of each of holder 8224, needle carrierassembly 8208, insertion element 8274, and on-skin sensor assembly 360may be specifically designed to reduce or substantially eliminate atendency of needle carrier assembly 8208, insertion element 8274, andon-skin sensor assembly 360 to prematurely detach from holder 8224 whilebeing driven in the distal direction during insertion. In someembodiments, a force exerted by spring 8212 may further be selected tobe sufficient for proper operation of applicator 8200, while not solarge as to further exacerbate such above described inertially triggereddetachment. In some embodiments, a spring (not shown) may be configuredto exert a force, in the distal direction for example, against a portionof needle carrier assembly 8208 sufficient to prevent needle carrierassembly 8208 from inertially triggered detaching from holder 8224during insertion.

FIG. 82D illustrates a state of applicator 8200 after retraction,according to some embodiments. As illustrated, wearable retentionelements 8272 a, 8272 b detach from on-skin sensor assembly 360 duringretraction. First spring 8212 has translated deployment sleeve 8206 inthe proximal direction. Because protrusion 8266 of needle carrierassembly 8208 is configured to contact deployment sleeve 8206 duringretraction, as deployment sleeve 8206 is driven in the proximaldirection, so is needle carrier assembly 8208 and insertion element8274. In some embodiments, it is this proximal translation that causeswearable retention elements 8272 a, 8272 b to detach from on-skin sensorassembly 360. Since spring 8212 pushes holder 8224 in the distaldirection and deployment sleeve 8206, needle carrier assembly 8208 andinsertion element 8274 in the proximal direction, insertion element 8274is locked, safely, in the second proximal retracted position.

Although not shown in FIGS. 82A-82D, applicator 8200 may furthercomprise a displacement-based lockout feature that prevents deploymentsleeve 8206 from translating in the proximal direction, therebypreventing retraction, until holder 8224 has translated at least apredetermined distance in the distal direction. Such adisplacement-based lockout feature may operate substantially asprotrusions 7546, 8146 previously described in connection with FIGS. 75Aand 81A-81D. For example, such a protrusion may extend in the proximaldirection from one or more of holder 8224 or needle carrier assembly8208 and may be configured to be in physical contact with deploymentsleeve retention elements 8262 a, 8262 b at least until holder 8224 orneedle carrier assembly 8208 has translated at least the predetermineddistance in the distal direction, thereby preventing inertial (i.e.,reaction force generated by the acceleration of mass) or accidentalactivation of applicator 8200, for example, due to concussive shock fromdropping applicator 8200.

During manufacture, applicator 8200 may be assembled in stages. Forexample, and not limitation, if present, first barrier layer 7192 orsimilar may be affixed to housing 8202. Insertion element 8274 may becoupled to needle hub 7150, if present, which may then be coupled toon-skin sensor assembly 360. If needle hub 7150 is not present,insertion element 8274 may be coupled directly to on-skin sensorassembly 360. Needle carrier assembly 8208 may be at least partlydisposed within deployment sleeve 8206 and spring 8212 may be placedinto holder 7124. Deployment sleeve 8206 and needle carrier assembly7108 may be disposed into holder 7124 and attached to needle hub 7150,if present, or directly to insertion element 8274 if needle hub 7150 isnot present, and to on-skin sensor assembly 360 via wearable retentionelements 8272 a, 8272 b. The assembly including holder 8224, deploymentsleeve 8206 and needle carrier assembly 8208 may then be installed intohousing 8202. If present, second barrier layer 7194 or similar may beaffixed to housing 8202. If a separate element, activation element 8204may then be disposed into housing 8202. Any labeling, sterilizing and/orpackaging may then be applied to applicator 8200.

FIGS. 83-85 illustrate several alternatives for activation elements inan applicator. Such alternatives may be directly applied to anyapplicator described in this disclosure, especially, though not in anyway limited to, applicators 7100, 8100 and 8200 described above.

FIG. 83 illustrates a cross-sectional view of an applicator 8300comprising a deformable layer 8305 disposed over an activation element8304, according to some embodiments. Although activation element 8304 isshown on a side of an outer housing 8301, any other suitable locationfor deformable layer 8305 and activation element 8304 is contemplated,e.g., a top, a high side, a low side of outer housing 8301. In someembodiments, deformable layer 8305 may be molded over activation element8304. In some other embodiments, deformable layer 8305 may be glued orwelded over activation element 8304, for example, utilizing ultrasonic,laser, radio frequency, heat stake welding processes, or any othersuitable process. In some embodiments, deformable layer 8305 maycomprise a film, an elastomer, a plastic or any other material withsufficient deformability to allow activation of activation element 8304as well as to provide an air and/or fluid-tight sealed surface overactivation element 8304.

FIG. 84 illustrates a perspective view of an applicator 8400 utilizing atwist-to-activate activation mechanism, according to some embodiments.Applicator 8400 comprises an outer housing 8401 and an inner housing8402. In some embodiments, outer housing 8401 and inner housing 8402may, together, comprise an activation element in that applicator 8400 isactivated by pushing down on applicator 8400 with sufficient force toimmobilize inner housing 8402 against the skin of the host as outerhousing 8401 is twisted with respect to inner housing 8402. Such adesign ensures applicator 8400 is pressed against the skin of the hostwith at least a minimum force, which can be designed to a particulardesired threshold based on, for example, a predetermined amount of forcethat ensures proper seating and orientation of applicator 8400 for use,the friction coefficient between inner housing 8402 and the skin of thehost, as well as based on the twisting force to trigger applicator 8400.

FIG. 85 illustrates a cross-sectional view of an applicator 8500comprising a top-mounted activation element 8504, according to someembodiments. In some embodiments, activation element 8504 may compriseany type of activation element described in this disclosure, including,but not limited to, a dome-shaped button. In some embodiments, such adome-shaped button may comprise a deformable material, as previouslydescribed in connection with FIG. 83 or, alternatively, may besufficiently rigid to hold its form when pressed or otherwise utilizedby the host.

Insertion Element Embodiments

Several embodiments of an insertion element, as previously describedherein, will now be described in connection with at least FIGS. 47-50,in which the insertion element is illustrated as being a needle.

FIG. 47 illustrates a cross-sectional view of a kinked needle 4774 foruse in an applicator for an analyte sensor system, according to someembodiments. Kinked needle 4774 may have at least two substantiallystraight portions 4790, 4792 with a bend 4796 between each substantiallystraight portion such that an angle 4796 between the substantiallystraight portions is substantially optimized to reduce lateral motion ofa tip of needle 4774 through the skin of the host as needle 4774 tracesan arc during activation.

FIGS. 48A-48B illustrate a cross-section and a plan view, respectively,of a flared open-sided needle 4874 for use in an applicator for ananalyte sensor system, according to some embodiments. Although FIGS.48A-48B illustrate open-sided needle 4874 having a C-shapedcross-section, the open-sided needle 4874 may have any shapedcross-section, e.g., a C-shape, a U-shape, a V-shape. FIG. 48Aillustrates a cross-section of an open-sided needle 4874 having at leastone flared edge 4876. For example, flared edge 4876 may be flared in alateral direction from a longitudinal centerline of open-sided needle4874. Such a flared edge 4876 may prevent or substantially reduce theincidence of damage to sensor 138 (e.g., FIG. 1) caused by sharp edgesof the open-sided needle coming in contact with sensor 138 before orduring insertion into the skin of a host.

FIG. 48B illustrates a plan view of open-sided needle 4874. Open-sidedneedle 4874 is illustrated as formed with an end opposite its tip havinga needle skirt 4878. Needle skirt 4878 may aid directing sensor 138 intothe needle lumen to assist with loading of sensor 138 and/or reduce theopportunity for damage of sensor 138 during use and/or loading.

FIG. 49 illustrates a perspective view of a deflected-tip needle 4974for use in an applicator for an analyte sensor system, according to someembodiments. Deflected-tip needle 4974 may comprise a substantiallystraight shaft having a substantially curved tip 4980, such that anangle of entry of deflected-tip needle 4974 is offset from thesubstantially straight shaft. Such an angle offset of the substantiallycurved tip 4980 may be particularly useful for reducing tissue damageand insertion resistance for applicators such as applicator 2500, aspreviously described in connection with FIGS. 25-28H, that have aninsertion path for the insertion element that is a substantially curvedpath. The substantially curved tip 4980 may steer deflected-tip needle4974 in the direction of the substantially curved insertion path,thereby reducing tissue damage caused by lateral movement of the needlewith respect to its direction of extension. FIG. 49 illustrates amagnified view 4950 of the curved tip 4980.

FIG. 50 illustrates a curved needle 5074 for use in an applicator for ananalyte sensor system, according to some embodiments. As shown, curvedneedle 5074 has a profile that is substantially curvilinear. Such acurvilinear profile may be particularly useful for reducing tissuedamage and insertion resistance for applicators such as applicator 2500,as previously described in connection with FIGS. 25-28H, that have aninsertion path for the insertion element that is a substantially curvedpath. The substantially curvilinear profile of needle 5074 may reducetissue damage caused by lateral movement of the needle with respect toits direction of extension. In some embodiments, the curvilinear profileof needle 5074 may substantially track or trace the insertion path forthe applicator, thereby substantially eliminating, or at least greatlyreducing, lateral movement of the needle with respect to the skin of thehost. In some embodiments, sensor 138 of on-skin sensor assembly 160 mayhave a curvilinear profile also, thereby allowing sensor 138 to restwithin a portion of curved needle 5074. In yet other embodiments, theinsertion element, for example a C-needle may have at least a portioncoated with a polymer that prevents damage to the tissue of the hostand/or to the sensor wire. Such a polymer may include, but is notlimited to, cyanoacrylate, epoxy, elastomeric polymers, urethanes or anyother suitable polymer.

In some embodiments, at least a sensing portion of sensor 138 may becoated with AgCl to improve the reference capacity of sensor 138.However, AgCl is a catalyst for corroding the metal in the insertionelement (e.g., open-sided needle). Accordingly, an AgCl coating onsensor 138 that comes into contact with the insertion element may beundesirable. One method of decreasing corrosion of sensor 138 and/or theinsertion element is to selectively remove or substantially decrease thecontent of AgCl on at least a proximal end of sensor 138 withoutsubstantially affecting the region of sensor 138 that is inserted intothe skin of the host. This may be accomplished by exposing the desiredportion of sensor 138 to a single frequency or multiple frequencies ofultraviolet radiation for a predetermined length of time and at apredetermined intensity. Such a process may be performed at any time,for example, during the skiving or singulation process. Another methodof removing AgCl is to expose the desired portion of sensor 138 to anammonia (NH₃) rinse at a desired concentration and for a desired lengthof time.

Sharp Protection

FIGS. 51A-51B illustrate cutaway views of a needle hub of an applicatorfor an analyte sensor system, according to some embodiments. FIG. 51Aillustrates a needle hub 5104, an insertion element 5174, a needle guard5102, a spring 5174, and a base 5130 of the applicator. First needle hub5104 may be fixed to a portion other than a tip of insertion element5174. Second needle hub 5102 may be configured to encapsulate the tip ofinsertion element 5174 and may comprise a material that insertionelement 5174 may pierce during deployment and/or may include an apertureor hole through which insertion element 5174 may pass. Spring 5106 isconfigured to keep a predetermined spacing between needle hub 5104 andneedle guard 5102 such that the tip of insertion element 5174 isencapsulated by needle guard 5102 when the predetermined spacing ismaintained. FIG. 51A illustrates a pre-activation position that may bereturned to after activation, under a returning force provided by spring5106, compressed during deployment of insertion element 5174. In someembodiments, the spring can be integrated into needle hub 5104 or needleguard 5102.

FIG. 51B illustrates needle hub 5104, insertion element 5174, needleguard 5102, spring 5174, and base 5130 of the applicator in the distal,deployed position. As shown, insertion element 5174 has been driventhrough needle guard 5102 and through an opening in base 5130. Sinceneedle hub 5104 is fixed to insertion element 5174, deployment ofinsertion element 5174 to the distal, deployed position closes thedistance between needle hub 5104 and needle guard 5102, therebycompressing spring 5106 (not shown in FIG. 51B). The energy stored incompressing spring 5106 is then utilized to force needle guard 5102substantially to its pre-activation position, thereby encapsulating thetip of insertion element 5174. It is contemplated that the featuresdescribed in FIGS. 51A-51B provide protection from needle stick hazards.

FIGS. 52A-52B illustrate a cross-sectional view and a top plan view,respectively, of an infusion cannula 5264 integrated into on-skin sensorassembly 160 of an analyte sensor system, according to some embodiments.In FIG. 52A, on-skin sensor assembly 160 is illustrated as includingsensor 138 and a fill port 5262 configured to receive a fluid, gel, ormedication (e.g., insulin) and cannula 5264 configured to deliver thefluid or gel through skin 130 of the host. In some embodiments, fillport 5262 comprises a septum material that maintains a seal for thetranscutaneous cannula and is capable of being pierced (e.g. by ahypodermic needle attached to a syringe) and allow for dosing themedication. This septum may be configured to self-seal after removal ofthe needle from the skin of the host. The infusion cannula and analytesensor may be inserted transcutaneously by the same applicator device.It is envisioned that a sharp (e.g. needle) placed within the lumen ofan infusion cannula and placed in parallel with the insertion element(e.g. attached to needle carrier assembly such as 508) for analytesensors may be added to the analyte applicators (e.g. applicator 500,800, 900, 1000, etc.). In FIG. 52B, on-skin sensor assembly 160 isillustrated as including an adhesive patch 5264 configured to adhereon-skin sensor assembly 160 to skin 130 of the host.

Sensor Retention Embodiments

In some embodiments, an insertion element, such as an open-sided needlemay be utilized to insert at least a portion of a sensor wire into theskin of a host. However, such embodiments generally operate best whenthe sensor wire remains seated in a channel of the open-sided needlebefore and during insertion. In addition, if the open-sided needle doesnot retain the sensor in the channel of the needle, the sensor may failto deploy into the tissue. Accordingly, FIGS. 53-59 illustrate severalembodiments of applicators that include sensor retention featuresconfigured to retain the sensor wire within a channel of the insertionelement at least before activation of the applicator. Althoughparticular applicators are shown, these retention features may beincorporated into any applicator described by this disclosure.

FIG. 53 illustrates a cross-sectional view of a sensor retentionmechanism for an applicator 5300 for an analyte sensor system, accordingto some embodiments. Applicator 5300 includes an applicator housing 5302having a retention feature 5384, for example a hook or protrusion.Applicator 5300 further includes on-skin sensor assembly 160 havingsensor 138, and an insertion element 5374 configured to guide sensor138. Applicator 5300 further comprises a retention element 5382, whichmay comprise an elastomeric band (e.g., a rubber band), a flexibleplastic, or metallic wire configured to press against an open side ofinsertion element 5374 thereby retention sensor 138 in insertion element5374. Upon activation of applicator 5300, an orientation or position ofone or more of retention feature 5384, retention element 5382 orinsertion element 5374 may be altered such that sensor 138 is no longeractively retained within insertion element 5374. For example, insertionelement 5374 may be configured to progress in the proximal direction atthe beginning of activation. The insertion element 5374 is withdrawnfrom the retention element allowing the retention element to recoil andclear the pathway of insertion for the on-skin sensor assembly.

FIG. 54 illustrates a perspective view of another sensor retentionmechanism 5482 for an applicator 5400 for an analyte sensor system,according to some embodiments. In FIG. 54, sensor retention mechanism5482 comprises a flexible or substantially rigid insert configured torest against applicator housing 5402 and against insertion element 5474,thereby retention sensor 138 in insertion element 5474. For example,retention mechanism 5482 may comprise a paper, plastic, elastomeric,metallic or polymeric sheet configured for removal before activation ofapplicator 5400. In some embodiments, retention mechanism 5482 may bemanufactured or cut to include a tab 5486 configured to press againstinsertion element 5474, thereby retention sensor 138 in insertionelement 5474.

In some embodiments, retention mechanism 5482 may be coupled to a linerof an adhesive patch of on-skin sensor assembly 160 such that when theliner is removed, in preparation for application of on-skin sensorassembly 160, retention mechanism 5482 may be simultaneously removed.

In some other embodiments, tab 5486 may be disposed at such an anglethat, rather than holding insertion element 5474 and sensor 138 betweentab 5486 and another portion of retention mechanism 5482, insertionelement 5474 and sensor 138 are configured to pierce and pass at leastpartially through tab 5486 such that sensor 138 is retained within achannel of insertion element 5474.

FIG. 55 illustrates a cutaway view of another sensor retention element5592 for an applicator 5500 for an analyte sensor system, according tosome embodiments. As shown, retention element 5592 may comprise a padcomprising foam, an elastomer, or any other suitable material, andinsertion element 5574 may be inserted at least partially into retentionelement 5592 such that sensor 138 (not shown in FIG. 55) is retainedwithin insertion element 5574. Retention element 5592 may be coupled toa bottom cap 5590 which is removable prior to activation of applicator5500.

FIGS. 56A-56B illustrate perspective views of another sensor retentionelement 5682 for an applicator 5600 for an analyte sensor system,according to some embodiments. Sensor retention element 5682 maycomprise a paddle or other surface configured to rest against insertionelement 5674 in a retention position, thereby retention sensor 138 inthe insertion element 5674. FIG. 56A illustrates sensor retentionelement 5682 in the retention position. Sensor retention element 5682 isconfigured to rotate, slide, or move away from insertion element 5674into a non-retaining position, thereby putting applicator 5600 in astate for activation. In some embodiments the arm of sensor retentionelement 5682 is configured to automatically move during or afteractivation into a non-retaining position via a linkage attached to anelement of the applicator. FIG. 56B illustrates sensor retention element5682 in the non-retaining position.

In some embodiments, sensor 138 may be retained in a channel of aninsertion element by an elastomeric band disposed around at least aportion of insertion element (e.g., an O-ring or any other flexible bandmaterial). The elastomeric band may be removed manually beforedeployment, or alternatively, may be removed from insertion elementautomatically by some operation of the applicator upon activation. Insome embodiments (e.g. applicator 500) the insertion element isconfigured to move in the proximal direction during the first portion(e.g. by changing the starting position of the scotch-yoke mechanism) ofthe insertion cycle. In this embodiment the elastomeric element is ableto clear the distal tip of the insertion element and recoil to clear thepathway of insertion of the on skin assembly.

In some other embodiments, sensor 138 may be retained in a channel of aninsertion element by a foam, paper, cardboard, plastic, polymeric tabconfigured to be pierced by insertion element such that the tab isdisposed substantially around a tip of insertion element, therebyretaining sensor 138 in the channel of the insertion element. The tabmay be removed manually before deployment, or alternatively, may beremoved from insertion element automatically by some operation of theapplicator upon activation.

FIG. 57 illustrates a perspective view of yet another sensor retentionelement 5782 for an applicator for an analyte sensor system, accordingto some embodiments. Sensor retention element 5782 includes a needle hub(not shown in FIG. 57) configured to guide insertion element 5774 (e.g.,a C-needle), which is it turn configured to guide sensor 138. A flexiblesleeve comprising a first portion 5706 a and a second portion 5706 b isdisposed over sensor 138 and insertion element 5774, thereby retainingsensor 138 in insertion element 5774. Upon activation, the needle hub isconfigured to drive insertion element 5774 in the distal direction,thereby splitting the flexible sleeve and separating first portion 5706a and second portion 5706 b. Once split, the flexible sleeve may nolonger retain sensor 138 in insertion element 5774.

FIG. 58 illustrates a perspective view of yet another sensor retentionelement 5882 for an applicator for an analyte sensor system, accordingto some embodiments. Sensor retention element 5882 includes a needle hub(not shown in FIG. 58) configured to guide insertion element 5874 (e.g.,a C-needle), which is it turn configured to guide sensor 138. A flexiblesleeve comprising a first portion 5806 a and a second portion 5806 b isdisposed over sensor 138 within a channel of insertion element 5874,thereby retaining sensor 138 in insertion element 5874. Upon activation,the needle hub is configured to drive insertion element 5874 in thedistal direction, thereby splitting the flexible sleeve and separatingfirst portion 5806 a and second portion 5806 b. Once split, the flexiblesleeve may no longer retain sensor 138 in insertion element 5874.

FIGS. 59A-59B illustrate cutaway views of yet another sensor retentionelement for an applicator for an analyte sensor system, according tosome embodiments. FIG. 59A illustrates a position of on-skin sensorassembly 160, an insertion element 5974 guiding sensor 138, and acannula (e.g. a tube such as PTFE, PE, polymer, metallic, etc.) 5962,configured to retain sensor 138 in an open sided insertion element 5974,during and before applicator activation. In FIG. 59A, cannula 5962 maybe coupled to on-skin sensor assembly 160 or at least configured to bedriven to the distal inserted position along with on-skin sensorassembly 160.

FIG. 59B illustrates on-skin sensor assembly 160, sensor assembly 138,and cannula 5962 in the inserted distal position with respect to skin130 of the host, insertion element 5974 having been retracted to theproximal retracted position (not shown in FIG. 59B). As shown, sensor138 may be inserted and disposed through cannula 5962, into skin 130 ofthe host. Cannula 5962 may provide strain relief and a minimum bendradius for sensor 138, thereby reducing the probability of damage tosensor 138 during deployment and operation. A significant portion of theelongated body of the analyte sensor may extend subcutaneously beyondthe cannula so as not to interfere with sensor function.

On-Skin Sensor Assembly Features

FIG. 68 illustrates a perspective view of an on-skin sensor assembly6860, which may include a base 6828. An adhesive patch 6826 can couplethe base 6828 to the skin 6830 of the host. In some embodiments, theadhesive patch 6826 may comprise an adhesive suitable for skin adhesion,for example a pressure sensitive adhesive (e.g., acrylic, rubber-based,or other suitable type) bonded to a carrier substrate (e.g., spun lacepolyester, polyurethane film, or other suitable type) for skinattachment, though any suitable type of adhesive is also contemplated.An on-skin sensor assembly 6860 may comprise an electronics unit 6840(e.g., a transmitter) which may further comprise a glucose sensor module6834 coupled to a glucose sensor 6838 and to base 6828.

The applicator system can couple adhesive patch 6826 to skin 6830. Theglucose sensor module 6834 may be secured to base 6828 (e.g., viaretention elements such as snap fits and/or interference features,adhesive, welding, etc.) to ensure glucose sensor 6838 is coupled tobase 6828. In alternative embodiments, the sensor module 6834 and base6828 are preassembled or manufactured as a single component.

After on-skin sensor assembly 6860 is applied to a user's skin, a user(or an applicator) can couple electronics unit 6840 (e.g., atransmitter) to on-skin sensor assembly 6860 via retention elements suchas snap fits and/or interference features. Electronics unit 6840 canmeasure and/or analyze glucose indicators sensed by glucose sensor 6838.Electronics unit 6840 can transmit information (e.g., measurements,analyte data, glucose data) to a remotely located device (e.g., 110-114shown in FIG. 1).

On-skin sensor assembly 6860 may be attached to the host with use of anapplicator adapted to provide convenient and secure application. Such anapplicator may also be used for attaching electronics unit 6840 to base6840, inserting sensor 6838 through the host's skin, and/or connectingsensor 6838 to electronics unit 6840. Once electronics unit 6840 isengaged with the base and sensor 6838 has been inserted into the skin(and is connected to the electronics unit 6840), the sensor assembly candetach from the applicator.

FIG. 69 illustrates a perspective view of electronics unit 6840 coupledto base 6828 via retention elements such as snap fits and/orinterference features. In some embodiments, electronics unit 6840 andbase 6828 are coupled by adhesive, welding, or other bonding techniques.Adhesive patch 6826, on a distal face of base 6828, is configured tocouple sensor assembly 6860 to the skin.

Reverting to on-skin sensor assembly 160 as previously described inconnection with FIG. 1, FIG. 70 illustrates a perspective view ofon-skin sensor assembly 6860. On-skin sensor assembly 6860 may bedisposable or reusable. FIG. 70 further illustrates electronics unit6840 coupled to a base 6828, and adhesive patch 6826 configured to beattached to on-skin sensor assembly 6860, which, when combined, may beheld within the applicator. Adhesive patch 6826 may or may not have anon-adhesive liner when held in the applicator.

Further, with respect to any of on-skin sensor assembly 160, 260, 360 ofFIGS. 1 and 2A-4, or on-skin sensor assembly 6860 of FIGS. 68-70,on-skin sensor assembly 160, 260, 360, 6860 is subjected to stress onportions of sensor 138, 238, 338, 6838 that are bent as the direction ofextension of sensor 138, 238, 338, 6838 transitions from substantiallyhorizontal, within on-skin sensor assembly 160, 260, 360, 6860 tosubstantially vertical, at the interface between on-skin sensor assembly160, 260, 360, 6860 and skin 130. FIGS. 58-63 describe severalembodiments that minimize the incidence of sensor damage as well as hostdiscomfort at this interface. While the following description mayidentify portions of on-skin sensor assembly 160 of FIG. 1, suchdescription may be equally applicable to on-skin sensor assembly 260,360, 6860 of FIGS. 2A-4, and 68-70.

FIG. 60 illustrates a cutaway view of on-skin sensor assembly 160 havingat least a portion of sensor 138 potted in a flexible material,according to some embodiments. On-skin sensor assembly 160 is shown asincluding at least sensor electronics 140, an insertion element 6074,such as a C-needle for example, passing through an opening in on-skinsensor assembly 160, and sensor 138 coupled or couplable to sensorelectronics 140 at a first end, and having a portion that is bent alonga bend radius such that a portion of sensor 138 beyond the bend isnested within or against insertion element 6074. Sensor 138 is furtherillustrated as having a flexible material 6002, e.g., an elastomericmaterial such as silicone, disposed around at least a portion of thebend in sensor 138. Flexible material 6002 may operate as astrain-relief element by limiting the bend radius of the bend to somepredetermined minimum radius that substantially reduces or eliminatesdamage to sensor 138. In some embodiments, flexible material 6002 mayextend to the hole through which sensor 138 passes at the on-skin sensorassembly-to-skin interface, which further provides a seal from moistureingress to on-skin sensor assembly 160. In some embodiments, a dedicatedseal comprising a flexible material may be provided at the hole throughwhich sensor 128 passes in addition to or as an alternative to flexiblematerial 6002.

FIG. 61 illustrates a cutaway view of on-skin sensor assembly 160comprising an open cavity configured to allow a larger bend radius insensor 138, compared to that shown in FIG. 60, according to someembodiments. On-skin sensor assembly 160 is shown as including at leastsensor electronics 140, an insertion element 6174, such as a C-needlefor example, passing through an opening in on-skin sensor assembly 160,and sensor 138 coupled or couplable to sensor electronics 140 at a firstend, and having a portion that is bent along a bend radius such that aportion of sensor 138 beyond the bend is nested within or againstinsertion element 6174. A bottom of on-skin sensor assembly 160 furtherincludes an open cavity 6102. Open cavity 6102 allows sensor 138 to bendalong a larger minimum bending radius than would be possible for anon-skin sensor assembly that does not include open cavity 6102. Sensor138 is shown in FIG. 61 as initiating this bend in advance of reachingopen cavity 6102 and arcing in an upward direction at the beginning ofthe bend, further increasing the potential minimum bend radius of sensor138. Such a larger bend radius reduces stress and strain on sensor 138,thereby reducing the probability of damage to sensor 138.

Open cavity 6102 may further promote healing of the open wound caused byinsertion of sensor 138 by insertion element 6174 by providing accessair access that improves drying of the wound site. Although not shown inFIG. 61, on-skin sensor assembly 160 may further include a porous,woven, or spun lace material configured to wick away moisture fromsweating or any other source, such as blood from the wound. Open cavity6102 would further provide a location for small amounts of this liquid,e.g., blood, to collect, thereby preventing it from seeping out andbeing visible to the host. Although not shown in FIG. 61, sensor 138 mayfurther include flexible material 6002, e.g., silicone, disposed aroundat least a portion of the bend in sensor 138 and/or a seal at the holethrough which sensor 138 passes, as previously described in connectionwith FIG. 60.

FIG. 62 illustrates a cutaway view of on-skin sensor assembly 160comprising an open cavity configured to allow a larger bend radius insensor 138, compared to that shown in FIG. 60, according to someembodiments. On-skin sensor assembly 160 is shown substantially aspreviously described in connection with FIG. 61, however, sensor 138 isshown as initiating the upward bend upon reaching, rather than inadvance of reaching, open cavity 6102. Although not shown in FIG. 62,sensor 138 may further include flexible material 6002, e.g., silicone,disposed around at least a portion of the bend in sensor 138 and/or aseal at the hole through which sensor 138 passes, as previouslydescribed in connection with FIG. 60. Such a larger bend radius reducesstress and strain on sensor 138, thereby reducing the probability ofdamage to sensor 138.

FIG. 63 illustrates a cutaway view of on-skin sensor assembly 160comprising an open cavity configured to allow a larger bend radius insensor 138, compared to that shown in FIG. 60, according to someembodiments. Such a larger bend radius reduces stress and strain onsensor 138, thereby reducing the probability of damage to sensor 138.On-skin sensor assembly 160 is shown substantially as previouslydescribed in connection with FIG. 61, however, sensor 138 is shown asinitiating a bend upon reaching, rather than in advance of reaching,open cavity 6102 and this bend is substantially in the downwarddirection, rather than first in an upward direction. Although not shownin FIG. 63, sensor 138 may further include flexible material 6002, e.g.,silicone, disposed around at least a portion of the bend in sensor 138and/or a seal at the hole through which sensor 138 passes, as previouslydescribed in connection with FIG. 60.

In yet other embodiments, at least a portion of sensor 138 may have abraided polyurethane material disposed thereon to provide further strainrelief. In addition, or in the alternative, additional materials such asan elastomer, flexible adhesive, or other braided or molded polymermaterial may be disposed thereon, in some embodiments, at least on thebend in sensor 138 and/or at a transition into on-skin sensor assembly160, to provide further strain relief. It is contemplated that thecomponents and features described above and/or with respect to FIGS.60-63 can be implemented in other on-skin sensor assemblies describedherein, such as on-skin sensor assembly 260 and 360.

In addition, during pressure fluctuations, such as at high altitude orvacuum during sterilization processes for example, air present withinthe applicator may exert a deforming force on on-skin sensor assembly160. Although not shown in any of FIGS. 60-63, in some embodiments,on-skin sensor assembly 160 may have at least a portion formed with areduced thickness and, therefore, reduced strength and rigidity, suchthat when applicator 460 is exposed to such pressure fluctuations, theportions having the reduced thickness expand in a controlled manner,thereby reducing or eliminating damage that would otherwise occur toon-skin sensor assembly 160 due to undesirable uncontrolled expansion ofon-skin sensor assembly 160. Such a feature may be present in theapplicator housing of any applicator described herein.

FIGS. 64A-64B illustrate an optional battery connection feature foron-skin sensor assembly 160, 260, 360 in accordance with someembodiments. FIG. 64A illustrates a storage mode, pre-activation.On-skin sensor assembly 160 is illustrated as including a battery 6410configured to power at least sensor electronics (e.g.,transmitter/sensor electronics 140, see FIG. 1). On-skin sensor assembly160 further includes an electrical contact 6402, configured tophysically and electrically contact battery 6410, an electricallyinsulating material 6404 (e.g., polyethylene terephthalate (PET), or anyother electrically insulative material) disposed between electricalcontact 6402, and a flexible material 6406 (e.g., ductile PET, TPSiV® orany other suitable material) coupled to on-skin sensor assembly 160 andto electrically insulating material 6404. In operation, pre-activation,electrically insulating material 6404 prevents electrical contactbetween electrical contact 6402 and battery 6410, maintaining on-skinsensor assembly 160 in an unpowered storage mode that prevents batterydrain before deployment. During activation, some portion 6408 ofapplicator may be configured to push down on flexible material 6406,which is physically coupled to electrically insulating material 6404,thereby shifting electrically insulating material 6404 such thatelectrical contact 6402 comes into electrical contact with battery 6410and shifting on-skin sensor assembly 160 into a battery connectedoperational mode, as will be shown in more detail in connection withFIG. 64B.

FIG. 64B illustrates the battery connected, operational mode of on-skinsensor assembly 160, 260, 360 discussed in FIG. 64A. Portion 6408 ofapplicator is illustrated as having pushed down or deformed flexiblematerial 6406 and moved electrically insulating material 6404 laterallysuch that electrical contact 6402 is in electrical contact with battery6410.

FIGS. 88A-88B illustrate another optional battery connection feature foron-skin sensor assembly 160, 260, 360 in accordance with someembodiments. FIGS. 88A illustrates a first perspective view of a batterysocket 8804 configured to hold a coin battery 8810 (see FIG. 88B),according to some embodiments. FIG. 88B illustrates a second perspectiveview of the battery socket 8804, according to some embodiments. Batterysocket 8804 comprises a first terminal comprising a tab 8806, configuredto make physical and electrical contact with one of a positive terminalor a negative terminal of battery 8810. Battery socket 8804 furthercomprises a second terminal comprising one or more clips 8808 configuredto make physical and electrical contact with the other of the positiveterminal or the negative terminal of battery 8810. In some embodiments,a portion of a PCB 8802 may insulate tab 8806 from the one or more clips8808. In some embodiments, battery socket 8804 may be soldered to PCB8802 to provide electrical and/or structural connections between batterysocket 8804 and one or more electrical components on PCB 8802. In someembodiments, PCB 8802 may comprise a single unitary piece. In someembodiments, battery 8810 may be secured to battery socket 8804 duringassembly of on-skin sensor assembly 160, 260, 360. In some embodiments,battery 8810 may be secured to tab 8806 via one or more tack welds. Insome embodiments, battery 8810 may be additionally or alternativelysecured to tab 8806 utilizing a spring, a piece of foam, or any otherelement disposed between battery 8810 and a housing or other portion ofon-skin sensor assembly 160, 260, 360 and configured to push or retainbattery 8810 against tab 8806. In some embodiments, battery 8810 mayadditionally or alternatively be secured to the one or more clips 8808via one or more respective tack welds.

Sterilization, Packaging, and Sealing Embodiments

For any of the embodiments of applicators expressly described herein,sterilization, packaging, and/or sealing features may also be included.In some embodiments, a user removing the applicator from its packagingand/or its sterilization features may partially or fully energize theapplicator (e.g., load unloaded springs). For example, motions such aspulling, twisting, pushing, or tilting required to remove an applicatorfrom its packaging or to remove one or more sterilization and/or sealingfeatures from the applicator may be harnessed to load partially unloadedor fully unloaded springs within the applicator. Such features wouldprovide a benefit in that less energy would have to be stored in thesprings of the applicator during its shelf life, prior to its use.Examples of sterilizing, sealing and packaging features contemplated forinclusion with any applicator described herein are described more fullyin U.S. patent application Ser. No. 16/011,527, which is incorporatedherein by reference it its entirety.

FIG. 67 illustrates exemplary sterilization, packaging and sealingfeatures of an applicator configured to apply an on-skin sensor assemblyto skin of a host, according to some embodiments. In some embodiments,the applicator (e.g. applicator 500, 800, 900, 1000, etc.). mayincorporate features such as sterile barrier, tamper evidence, devicesealing and/or device protection. Methods of sterile barrier, tamperevidence, device sealing, and/or device protection are also described inU.S. patent application Ser. No. 16/011,527. Non-limiting examples mayinclude a tamper evident feature 6810 (e.g. FIGS. 1A-5B), a capsulesealing feature 6820 (e.g. FIGS. 1A-3C), a gas permeable 6830 and/ornon-gas permeable sterile barrier 6840 (e.g. FIGS. 1A, 2B, 4B, 5B, 7B,8B, 9, 11A, 13A, 15A-27B, 29-30B), or device protection feature 6850(e.g. FIG. 1A-24B).

Tamper evident sealing or other tamper evidence features 6810 allow aconsumer to identify when an applicator has been previously used orcontainment has been breached and, thus, avoid using an applicator thatmay be faulty or pose an increased health risk if used. Non-limitingexamples of tamper evident features 6810 also described in U.S. patentapplication Ser. No. 16/011,527, include ring, peelable layer,perforated tab, adhesive mounted tab, and/or twist-off collar. Thesefeatures may be incorporated in current embodiments within an applicatorhousing (e.g. 502) or additional bodies added to the applicator assembly(e.g. cap, shell, lid, tab, peelable layer, frangible, ring, etc.).

Capsule sealing features 6820 create an enclosed volume from multiplecomponents. Non limiting examples of capsule sealing features alsodescribed in U.S. patent application Ser. No. 16/011,527, include one ormore removable caps on the top (e.g., proximal) or bottom (e.g., distal)ends of the applicator, through one or more trigger mechanismscomprising integrated caps, through one or more sealing layers thatcover one or more orifices, apertures or vents of the applicator,through sterilizable gas-permeable polymers, through sterilizablegas-permeable trigger mechanisms, through protective cups, or anycombinations of the same, described in more detail with at least some ofFIGS. 1A-33. These features may be incorporated in current embodimentswithin an applicator housing (e.g. 502) or additional bodies added tothe applicator assembly (e.g. cap, shell, lid, tab, peelable layer,elastomer, O-ring, adhesive, button, etc.).

Gas permeable sterile barriers 6830 allow a device to create an enclosedvolume that is permeable to a gas (e.g. a sterilization gas) andmaintain a microbial barrier to an exterior volume. A non-gas permeablesterile barrier 6840 performs the same functions of a gas permeablesterile barrier with the additional function of blocking gasses than mayhave deleterious effects (e.g. water vapor). Gas permeable 6830 and/ornon-gas permeable sterile barrier 6840 may be used in conjunction orindependently as also described in U.S. patent application Ser. No.16/011,527. These features may be incorporated in current embodimentswithin an applicator housing (e.g. 502) or additional bodies added tothe applicator assembly (e.g. cap, shell, lid, tab, peelable layer,packaging, seal, button, etc.).

Device protection features 6850 may be adapted to protect functionalcomponents of applicators (e.g. applicator 500, 800, 900, 1000, etc.).Functions may include inadvertent activation prevention, dropprotection, needle damage protection, or other functions also disclosedin U.S. patent application Ser. No. 16/011,527. These features may beincorporated in current embodiments within an applicator housing (e.g.502) or additional bodies added to the applicator assembly (e.g. cap,shell, lid, tab, peelable layer, frangible, packaging, seal, button,etc.).

Methods of Applying an On-Skin Sensor Assembly to Skin of a Host

FIG. 65 illustrates a flowchart 6500 of a method for applying an on-skinsensor assembly to skin of a host, according to some embodiments. Stepsin flowchart 6500 may be performed utilizing any applicator aspreviously described in connection with any of the previous FIGs.Although certain steps are set forth below, a method of using such anapplicator may comprise more, fewer, or different steps, in the same ordifferent order from that set forth below.

Flowchart 6500 illustrates block 6502, including providing an applicatorcomprising an applicator housing, a needle carrier assembly comprisingan insertion element configured to insert a sensor of the on-skin sensorassembly into the skin of the host, a holder releasably coupled to theneedle carrier assembly and configured to guide the on-skin sensorassembly while coupled to the needle carrier assembly, a drive assembly,and an activation element. In some embodiments, the distal direction andthe proximal direction extend along an insertion axis of the insertionelement.

Flowchart 6500 further illustrates block 6504, including activating anactivation element, wherein activating the activation element causes thedrive assembly to drive the insertion element in a distal direction to adistal insertion position and in a proximal direction from the distalinsertion position to a proximal retraction position, thereby insertingthe sensor of the on-skin sensor assembly at least partially into theskin of the host.

FIG. 89 illustrates a flowchart 8900 of another method for applying anon-skin sensor assembly to skin of a host, according to someembodiments. Steps in flowchart 8900 may be performed utilizing anyapplicator as described in connection with any FIGs., for example butnot limitation, FIGS. 71-88. Although certain steps are set forth below,a method of using such an applicator may comprise more, fewer, ordifferent steps, in the same or different order from that set forthbelow.

Flowchart 8900 illustrates block 8902, including providing an applicatorcomprising a housing having an activation element, an insertionassembly, and a retraction assembly.

Flowchart 8900 further illustrates block 8904, including activating theactivation element, wherein activating the activation element causes theinsertion assembly to translate a needle carrier assembly and theon-skin sensor assembly in a distal direction from a proximal positionto a distal insertion position, thereby inserting a sensor of theon-skin sensor assembly at least partially into the skin of the host,and the retraction assembly to translate the needle carrier assembly ina proximal direction from the distal inserted position to a proximalretracted position, the retraction assembly configured to activate inresponse to on-skin sensor assembly contacting the skin of the host. Insome embodiments, the distal direction and the proximal direction extendalong an insertion axis of an insertion element of the applicator.

Exemplary Mechanisms for Applicator Features

FIG. 66 illustrates exemplary mechanisms for several features of anapplicator configured to apply an on-skin sensor assembly to skin of ahost, according to some embodiments. The mechanisms described inconnection with FIG. 66 are exemplary and not limiting.

For example, the feature activation element 6610 as used herein may beconsidered to include any type of mechanism that, when operated asintended, serves to activate a drive mechanism of an applicator and,thereby, apply an on-skin sensor assembly to skin of a host. Forexample, an activation element may include an element configured totrigger when pushed, pulled, switched, toggled, slid, triggered,deflected, rotated, deformed or flexed from a first position or state toat least a second position or state. General examples include but arenot limited to buttons, slides, hooks, switches, a flexible portion ofthe applicator housing itself, tabs, or strings. Moreover, althoughcertain embodiments of applicators are described herein as having anactivation element in a particular location, any applicator describedherein is also contemplated having one or more activation members in anyother position, e.g., a top, upper side, medial side, lower side, orbottom of the applicator. Moreover, in some embodiments, two or moreactivation elements may be operated in tandem in order to activate theapplicator. The above-described activation elements may be applied orutilized in connection with any applicator described herein.

The feature insertion element 6620 as used herein may be considered toinclude any type of mechanism that, when operated as intended, serves toinsert a sensor or sensor wire at least partially into a skin of a host.For example, an insertion element may include, but is not limited to, aregular, circumferential needle, an open sided-needle (e.g., FIGS.48A-48B), a needle with a deflected tip (e.g., FIG. 49), a curved, bentor kinked needle (e.g., FIGS. 47 and 50), a polymer-coated needle, ahypodermic needle, or the sensor or sensor wire tip itself

The feature retention element or on-skin sensor assembly retentionelement 6630 as used herein may be considered to include any type ofmechanism that, when operated as intended, serves to retain an on-skinsensor assembly in a particular position, orientation or constrain thefeature to a particular path of motion. For example, a retention elementmay include, but is not limited to, a hook, a claw, a tab, an arm, anundercut and snap feature, a press fit feature, a deformable and/orelastomeric element (as described in connection with any of FIGS. 5-7D,12-14E, 25-27E, 32A-37C and 41A-46), or any on-skin sensor assemblyretention element illustrated in U.S. patent application Ser. No.15/387,088 as described above.

The feature spring and/or energy source 6650 as used herein may beconsidered to include any suitable type of spring configured to storepotential energy when loaded and configured to release at least aportion of that stored potential energy to drive one or more portions ofan applicator as required or desired. For example, a spring may include,but is not limited to, a compression spring, which is configured tostore energy when compressed to less than its resting length (e.g., FIG.32), an extension spring, which is configured to store energy whenstretched to greater than its resting length (e.g., FIG. 21), a singleor double torsion spring (e.g., FIG. 12), clock spring or power spring,which are configured to store energy in torsional deformation of aportion of the spring from its resting profile, or a leaf spring (e.g.,FIGS. 22 and 25), which is configured to store energy in the physicaldeformation of the spring from its resting profile.

Insertion and/or retraction mechanisms 6660 may be considered to includeany suitable mechanism for causing a movement of an insertion element ina distal direction to a distal inserted position, and/or in a proximaldirection to a proximal retracted position. For example, such mechanismsmay include, but are not limited to, a scotch yoke mechanism (e.g., FIG.5) a barrel cam (e.g., FIG. 29), opposing springs mechanism, a reversetoggling mechanism comprising a lever having a first end, a second end,and a fulcrum at a point between the first and second ends (e.g., FIG.31), a flexible linkage (e.g., FIGS. 18-23), a spring linkage (e.g. FIG.12-14E), or any hinging or pivoting (e.g. FIG. 25-28H) apparatus thatoperates as described in this disclosure.

Energy storage 6640, for example, as potential energy stored in aspring, for any applicator described in this disclosure may bepre-loaded (e.g., in the factory or before provision to a user),mechanism loaded (e.g., some operation of the applicator loads thespring), or user loaded (e.g., the user provides energy in some form ofmotion that is utilized to store potential energy in a spring).

Sensor retention 6670 for any applicator described in this disclosuremay be user-removable (e.g., FIGS. 54, 57, 58), mechanism-removable(e.g., FIGS. 53, 56A-56B, 57 and 58), ex-vivo support feature (e.g.,FIGS. 55-58), or in-vivo support feature (e.g., FIGS. 59A-59B). Forexample, an elastomeric element such as a rubber band (see FIG. 53), afoam, rubber or other pad (see FIG. 55), a frangible element (see FIGS.57-58), an adhesive layer, or a wire.

Elements within each feature category (e.g., 6610, 6620, 6630, 6640,6650, 6660, 6670) are interchangeable for any applicator describedherein. For instance, applicator 500 shown in FIGS. 5-6H includes a pushbutton and deflecting arm activation element 504, an open-sided needleinsertion element 674, an undercut/snap feature 678 a, 678 b for on-skinsensor assembly 160 retention, a pre-loaded energy storage in which theenergy source is a single torsion spring 512, and a scotch yokeinsertion/retraction mechanism 510. However, in an alternativeembodiment, applicator 500 may instead include a switch/toggleactivation element, a curved/bent needle insertion element (e.g., 5074),a press fit on-skin sensor assembly retention, and an ex-vivo supportfeature sensor retention (e.g., FIGS. 55-58).

In another example, applicator 2500 shown in FIGS. 25-28H includes apush button and deflecting arm activation element 2504, an open-sidedneedle insertion element 2674, an undercut/snap feature (e.g., similarto 678 a, 678 b) on needle carrier assembly 2508 for on-skin sensorassembly 160 retention, a pre-loaded energy storage in which the energysource is a compression spring 2512 and leaf springs 2528, and a hingingor pivoting apparatus 2508, 2524. However, in an alternative embodiment,applicator 2500 may instead include a switch/toggle activation element,a curved/bent needle insertion element (e.g., 5074), a press fit on-skinsensor assembly retention, and an ex-vivo support feature sensorretention (e.g., FIGS. 55-58).

It should be appreciated that all methods and processes disclosed hereinmay be used in any glucose monitoring system, continuous orintermittent. It should further be appreciated that the implementationand/or execution of all methods and processes may be performed by anysuitable devices or systems, whether local or remote. Further, anycombination of devices or systems may be used to implement the presentmethods and processes.

Methods and devices that are suitable for use in conjunction withaspects of the preferred embodiments are disclosed in U.S. Pat. Nos.4,757,022; 4,994,167; 6,001,067; 6,558,321; 6,702,857; 6,741,877;6,862,465; 6,931,327; 7,074,307; 7,081,195; 7,108,778; 7,110,803;7,134,999; 7,136,689; 7,192,450; 7,226,978; 7,276,029; 7,310,544;7,364,592; 7,366,556; 7,379,765; 7,424,318; 7,460,898; 7,467,003;7,471,972; 7,494,465; 7,497,827; 7,519,408; 7,583,990; 7,591,801;7,599,726; 7,613,491; 7,615,007; 7,632,228; 7,637,868; 7,640,048;7,651,596; 7,654,956; 7,657,297; 7,711,402; 7,713,574; 7,715,893;7,761,130; 7,771,352; 7,774,145; 7,775,975; 7,778,680; 7,783,333;7,792,562; 7,797,028; 7,826,981; 7,828,728; 7,831,287; 7,835,777;7,857,760; 7,860,545; 7,875,293; 7,881,763; 7,885,697; 7,896,809;7,899,511; 7,901,354; 7,905,833; 7,914,450; 7,917,186; 7,920,906;7,925,321; 7,927,274; 7,933,639; 7,935,057; 7,946,984; 7,949,381;7,955,261; 7,959,569; 7,970,448; 7,974,672; 7,976,492; 7,979,104;7,986,986; 7,998,071; 8,000,901; 8,005,524; 8,005,525; 8,010,174;8,027,708; 8,050,731; 8,052,601; 8,053,018; 8,060,173; 8,060,174;8,064,977; 8,073,519; 8,073,520; 8,118,877; 8,128,562; 8,133,178;8,150,488; 8,155,723; 8,160,669; 8,160,671; 8,167,801; 8,170,803;8,195,265; 8,206,297; 8,216,139; 8,229,534; 8,229,535; 8,229,536;8,231,531; 8,233,958; 8,233,959; 8,249,684; 8,251,906; 8,255,030;8,255,032; 8,255,033; 8,257,259; 8,260,393; 8,265,725; 8,275,437;8,275,438; 8,277,713; 8,280,475; 8,282,549; 8,282,550; 8,285,354;8,287,453; 8,290,559; 8,290,560; 8,290,561; 8,290,562; 8,292,810;8,298,142; 8,311,749; 8,313,434; 8,321,149; 8,332,008; 8,346,338;8,364,229; 8,369,919; 8,374,667; 8,386,004; 8,394,021; 8,527,025;7,896,809; 9,119,528; and 9,119,529.

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The above description presents the best mode contemplated for carryingout the present invention, and of the manner and process of making andusing it, in such full, clear, concise, and exact terms as to enable anyperson skilled in the art to which it pertains to make and use thisinvention. This invention is, however, susceptible to modifications andalternate constructions from that discussed above that are fullyequivalent. Consequently, this invention is not limited to theparticular embodiments disclosed. On the contrary, this invention coversall modifications and alternate constructions coming within the spiritand scope of the invention as generally expressed by the followingclaims, which particularly point out and distinctly claim the subjectmatter of the invention. While the disclosure has been illustrated anddescribed in detail in the drawings and foregoing description, suchillustration and description are to be considered illustrative orexemplary and not restrictive.

All references cited herein are incorporated herein by reference intheir entirety. To the extent publications and patents or patentapplications incorporated by reference contradict the disclosurecontained in the specification, the specification is intended tosupersede and/or take precedence over any such contradictory material.

Unless otherwise defined, all terms (including technical and scientificterms) are to be given their ordinary and customary meaning to a personof ordinary skill in the art, and are not to be limited to a special orcustomized meaning unless expressly so defined herein. It should benoted that the use of particular terminology when describing certainfeatures or aspects of the disclosure should not be taken to imply thatthe terminology is being re-defined herein to be restricted to includeany specific characteristics of the features or aspects of thedisclosure with which that terminology is associated. Terms and phrasesused in this application, and variations thereof, especially in theappended claims, unless otherwise expressly stated, should be construedas open ended as opposed to limiting. As examples of the foregoing, theterm ‘including’ should be read to mean ‘including, without limitation,’‘including but not limited to,’ or the like; the term ‘comprising’ asused herein is synonymous with ‘including,’ ‘containing,’ or‘characterized by,’ and is inclusive or open-ended and does not excludeadditional, unrecited elements or method steps; the term ‘having’ shouldbe interpreted as ‘having at least;’ the term ‘includes’ should beinterpreted as ‘includes but is not limited to;’ the term ‘example’ isused to provide exemplary instances of the item in discussion, not anexhaustive or limiting list thereof; adjectives such as ‘known’,‘normal’, ‘standard’, and terms of similar meaning should not beconstrued as limiting the item described to a given time period or to anitem available as of a given time, but instead should be read toencompass known, normal, or standard technologies that may be availableor known now or at any time in the future; and use of terms like‘preferably,’ ‘preferred,’ ‘desired,’ or ‘desirable,’ and words ofsimilar meaning should not be understood as implying that certainfeatures are critical, essential, or even important to the structure orfunction of the invention, but instead as merely intended to highlightalternative or additional features that may or may not be utilized in aparticular embodiment of the invention. Likewise, a group of itemslinked with the conjunction ‘and’ should not be read as requiring thateach and every one of those items be present in the grouping, but rathershould be read as ‘and/or’ unless expressly stated otherwise. Similarly,a group of items linked with the conjunction ‘or’ should not be read asrequiring mutual exclusivity among that group, but rather should be readas ‘and/or’ unless expressly stated otherwise.

Where a range of values is provided, it is understood that the upper andlower limit, and each intervening value between the upper and lowerlimit of the range is encompassed within the embodiments.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity. The indefinite article ‘a’ or ‘an’ does not exclude aplurality. A single processor or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage. Anyreference signs in the claims should not be construed as limiting thescope.

It will be further understood by those within the art that if a specificnumber of an introduced claim recitation is intended, such an intentwill be explicitly recited in the claim, and in the absence of suchrecitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases ‘at least one’ and ‘one or more’ to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles ‘a’ or ‘an’ limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases‘one or more’ or ‘at least one’ and indefinite articles such as ‘a’ or‘an’ (e.g., ‘a’ and/or ‘an’ should typically be interpreted to mean ‘atleast one’ or ‘one or more’); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of ‘two recitations,’ without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to ‘at least one of A, B, and C, etc.’ is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., ‘a system having at least one ofA, B, and C’ would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to ‘at least one of A, B, or C, etc.’ is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., ‘a system having at leastone of A, B, or C’ would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase ‘A or B’ will be understood toinclude the possibilities of ‘A’ or ‘B’ or ‘A and B.’

All numbers expressing quantities of ingredients, reaction conditions,and so forth used in the specification are to be understood as beingmodified in all instances by the term ‘about.’ Accordingly, unlessindicated to the contrary, the numerical parameters set forth herein areapproximations that may vary depending upon the desired propertiessought to be obtained. At the very least, and not as an attempt to limitthe application of the doctrine of equivalents to the scope of anyclaims in any application claiming priority to the present application,each numerical parameter should be construed in light of the number ofsignificant digits and ordinary rounding approaches.

Furthermore, although the foregoing has been described in some detail byway of illustrations and examples for purposes of clarity andunderstanding, it is apparent to those skilled in the art that certainchanges and modifications may be practiced. Therefore, the descriptionand examples should not be construed as limiting the scope of theinvention to the specific embodiments and examples described herein, butrather to also cover all modification and alternatives coming with thetrue scope and spirit of the invention.

What is claimed is:
 1. An applicator for applying an on-skin sensorassembly to a skin of a host, the applicator comprising: a first bodyreleasably coupled to a needle; a second body releasably coupled to thefirst body by a frictional engagement; a spring configured to provide afirst force to the first body and second body, the first force drivingthe first body and second body in a distal direction; and wherein thefrictional engagement is configured to be decoupled by a counter forceapplied to the on-skin sensor assembly in an opposite direction of thefirst force.
 2. The applicator of claim 1, further comprising at leastone retention element configured to frictionally couple the second bodyto the first body.
 3. The applicator of claim 2, wherein the at leastone retention element is formed integral with the second body.
 4. Theapplicator of claim 3, wherein the at least one retention element isfrictionally engaged against a wall of the first body.
 5. The applicatorof claim 4, wherein the counter force decouples the frictionalengagement by displacing the at least one retention element from thewall of the first body.
 6. The applicator of claim 5, wherein the wallis a backstop.
 7. The applicator of claim 5, wherein the wall isconfigured to prevent the at least one retention element fromdeflecting.
 8. The applicator of claim 2, wherein the frictionalengagement is decoupled by the counter force exceeding a forcethreshold.
 9. The applicator of claim 8, wherein the force threshold isdetermined by the frictional force between the at least one retentionelement and the first body.
 10. The applicator of claim 9, wherein thethreshold is at least 0.5 lbf.
 11. The applicator of claim 9, whereinthe threshold is at least 1 lbf.
 12. The applicator of claim 1, whereinthe first body is configured to retract in a proximal direction upondecoupling of the frictional engagement.
 13. The applicator of claim 12,further comprising a second spring, the second spring configured todrive the first body in a proximal direction.
 14. The applicator ofclaim 13, wherein the second spring is retained from release by at leastone retention element of the second body.
 15. The applicator of claim 1,wherein the decoupling of the frictional engagement is configured to beindependent of a distance between the on-skin sensor assembly and adistal end of the applicator.
 16. The applicator of claim 15, whereinthe first body is configured to retract independent of the distancebetween the on-skin sensor assembly and the distal end of theapplicator.
 17. The applicator of claim 1, wherein the counter forceapplied to the on-skin sensor assembly is provided by the skin of thehost opposing the first force.
 18. The applicator of claim 17, whereinan interior of the applicator is configured to allow the skin of thehost to reside within the interior.
 19. The applicator of claim 1,wherein the needle is configured to be inserted into the skin apredetermined depth.
 20. The applicator of claim 1, wherein thefrictional engagement is configured to decouple at a range of distancesbetween the on-skin sensor assembly and a distal end of the applicator.